I'll start with the positive: location is awesome. The building itself is great, the lobby is quite extraordinary. It really looks like an old palazzo. The staff is very polite, competent and helpful. I had a specific request for New Year's Eve, and they delivered exactly. The room was spacious and clean. Wifi was freely available, signal wasn't very strong but it worked all right. New Year dinner was excellent, with nice music and a really good choice of wine.
Now for the problems: the place looks old and quaint. The rooms are freshly painted all right, but this is it. Furniture is antique. True, it gives the place a distinct patina, but too much of patina is not good. Moreover, there isn't much of furniture to start with. There are no shelves in the cupboard. My room was actually so big, and furniture so minimalist, that it felt like an empty room. The flat-screen TV was nice and large but, being situated in the opposite corner, it felt like watching a small screen. The beds are way too short (they probably are made for the average-sized man of the 19th century)
Bottom-line: the place needs massive refurbishment.
As mentioned, the staff is great, but there is not nearly enough of it. There is no concierge any longer (there was one back in 2005).
The worst thing was the breakfast. I have never seen such a limited choice, certainly not in a place which claims such a standing.
It is really a pity, because, with a proper overhaul, this could be the top address in Rome. Mandarin Oriental or Four Seasons could make wonders with it. As it stands, it is a massively overpriced place, which, despite the best efforts of its staff, is absolutely unworthy of anything above a 3 stars rating.

Grand Plaza location is excellent but the service is horrible. I paid $607 EU/night for a lovely jr suite with a balconey. The bed is so hard I did not sleep for 6 nights. The pillows are like lead; the sheets itch; the towels are holiday in quality; amenities are few and cheap in the bath. There is no concierge. No one answers the phone for room service. The front desk is run by one person who most of the time is rude. There is no doorman; one bellman for the hotel. They leave dirty glasses in the room. There is no evening maid service. They chain the hotel at midnight. They have no diea who their guests are and clearly don't care. It was a huge and very expensive mistake! Don't do it!

We went to Rome for my landmark birthday, with my toddler and other half.
We chose to splash out a little bit because of this, and chose this hotel due to the location and because of the reviews regarding it's grand decor.
I had already read a few reviews, so I knew not to expect perfect finishes to the decor.

On arrival, the reception staff were polite, but appeared slightly absentminded at times. It was difficult to tell if they were concentrating on what you were saying, as they appeared to be multitasking a lot of the time, and didn't make the time to gesture to acknowledge your existence. However, it was only a small grumble. The staff for the remainder of the stay were very attentive, very toddler friendly and helpful. We had to go to the bar to buy milk for our baby bottle, and the gentleman behind the bar was very friendly, polite and helpful enough to warm it up.

The room we were given was beautiful. It was a suite, and had a sofa bed, which we used for our toddler. The only bug bear was, after the first night, my son had a little accident on the bed, so we took the sheets off and left them on the floor of the bathroom, hoping they would understand that they needed replacing. Unfortunately, from the smell of the sheets later that night, they put those sheets back on the sofa bed, so we had to bring him into our bed that night.

The breakfast was included with our booking. It was a buffet, with some pastries, sausage and cereals. Not the best range of breakfast buffet I've had, but the room decor made up for it. It was like eating in the ballroom in the Sound of Music.

I definitely did not regret staying here. The location was perfect (round the corner from the spanish steps) and the grandiosity of the place was breath taking. We spent a while every day, just sitting and looking at it all.

Twin bedroom. Was surprised that room was more like a suite with walk in corridor and elegant sofa with very high ceiling. Room facing courtyard. Seemed freshly painted. Bathroom had a bathtub.
Breakfast room glamorous but somewhat overdecorated.
If you paid tax beforehand bring credit card receipt. Good location.