Although this is definitely not a five star hotel by the standards of other European countries, we really enjoyed our stay at the Senhora da Guia for two nights in the middle of September 2011. It is more like a good three star or possibly four star standard hotel. We found the staff friendly but the service was generally poor and very slow. Our bedroom, for two people, was small (probably more suited to one person) but clean and well equipped; the staff member who checked us in even admitted that the room was really too small for two people by saying it was "okay for two nights". The room was located in the block away from the main hotel, so was quiet and peaceful and we had a nice little terrace which caught the sunshine in the evening. We had dinner in the hotel on one evening and the food was absolutely superb and well priced. There was a bizarre, very slow system with the wine ... where only one of the serving staff could take the wine order and serve it, and the others absolutely couldn't take your wine order and pass it on to the wine guy. So we couldn't order our food and wine from the same person and if we needed a top-up of wine, we had to wait for the wine guy to come and fill the glasses (as the bottle was not on our table). The pool area is really lovely, with very comfortable sun loungers. However, it would be nice if the hotel offered waiter service by the pool. We had to go inside each time we wanted lunch, water, wine etc and I ended up bringing the empty glasses inside when the wind was blowing outside as no-one came to pick them up and I was worried they would get broken if they fell because of the wind. Also, on one of the days, one of the lbig sun umbrellas blew around the garden because of the strong wind for about 45 minutes before a staff member came out to put it back where it belonged. It is a bit too far to walk to the centre of Cascais (we tried it one evening... took over one hour), so the best option is to take a taxi; we paid anything between €5 and €6 each way).

We stayed here for four nights in June 2011 and had a very enjoyable time. The hotel is located a few kms from Cascais town, and a couple of hundred metres from the sea. There is a busy road at the front of the hotel, which seems to be part of the local cycling and jogging route, given the amount of locals indulging in these pastimes here. Once inside the hotel, the road is not visible nor audible due to the lie of the land and the layout of the hotel. The coastline at the front of the hotel consists entirely of steep and rugged cliffs so it is not possible to access the sea directly here. Still, it makes for a pleasant evening walk.
If you want to go to the beach, then it is necessary to go into Cascais itself. It is rather a long walk, especially with children, so a better option is a taxi (about EUR4 into Cascais from the hotel). There is a local bus passing the front of the hotel into Cascais but nobody seemed sure of the timetable.
The hotel itself was impeccable. The room was clean, spacious and airy. Our room was located in the block away from the main hotel, reception, restaurant, etc. and was very quiet. The view from our balcony was not great- the back yard- but other rooms have a garden view or sea view, for which you need to pay extra. We had dinner here every evening except one and enjoyed our meal each time. I am vegetarian and in this case the choice is somewhat limited but adequate for a short stay. The prices are excellent compared to restaurants of a similar standard in town. The restaurant has lovely views overlooking the Atlantic. What can be better than enjoying a great meal and a bottle of the local red whilst admiring a sunset over the Atlantic! There is even cheesey live music here occasionally.
We really enjoyed relaxing by the pool here. There is a pleasant, leafy garden adjoining the pool area so you can just lounge about here if you don't want to be right next to the pool. There is also a lovely shady area near the garden and pool where they serve drinks and snacks.
The staff in the hotel were enormously friendly and conscientious. No complaints here.
The hotel operates a limousine pick-up service at the airport for which they charged EUR60, one-way. Given that this is about a 60 min drive, that there can be long queues for taxis at the airport, that public transport out to here would be very difficult indeed, I think that this is a good option to take. In fact we had a luxury limousine to ourselves and a wonderful old man driving us, who was more than willing to give us a running commentary on all the sights as we passed by Lisbon on the road out to Cascais.
I can find no criticism of this hotel except that I don't really believe that it deserves five stars. For that you do normally need a bit more than what they offer here.

The official star system for hotels has always been something of an anachronism. It seems to be a system whereby you tot up the number of features regardless of quality. Please be assured there is no way this hotel deserves 5 stars, especially when you consider the generally high standard of hotels in Portugal.
The word that keeps occurring to me is "amateurish" . It is almost as if someone with no experience of running a hotel has decided to do so and thinks a few trendy features is all it takes, eg a nespresso machine.
Any of the shortcomings individually don't seem much but cumulatively they add up to a vastly overpriced poor experience. Some examples : the shower head by the swimming pool being so encrusted with green growth that it is probably a health risk - the tray underneath by the way matches it; the slight smell of drains mentioned by others, remains- at least in my room; Smart leather wastepaper baskets in room cheapened by black plastic sacks; Paper napkins (in a 5 star hotel!!); 9 euros per day if you want wireless Internet - double that if you want a fast connection; Staff friendly but most take little pride in their appearance - not helped by the male uniforms which you would normally find a dentist wearing (what's that about?), 3 star breakfast buffet, no turn down service .... The list goes on and on. Good points - the bed was reasonably comfortable - that's it ...
This hotel should be 3 star and charge accordingly. As a regular visitor to Portugal I can tell you that you can get far better value elsewhere.

My two friends and I recently traveled to Cascais and wanted to treat ourselves to a great boutique hotel. This is fantastic. It feels like a spa-- chill, relaxed. A lovely welcome, friendly staff and well decorated. My only complaint (and honestly, it would probably keep me from coming back) it is the outrageous daily prices they charge for internet. I frequently travel all over the world and in this day free WiFi is a given. We had just come from a 50euro/night guesthouse in Ericeira where it was free. They do have a free 'business center' with one computer, but who wants to wait in a dripping bathing suit while someone finishes up checking their email? The fee is in poor taste for such a lovely hotel.