The location is very good for easy access from the railway station (trains from the airport). It is also walking distance to all shopping and sight-seeing. The location is very quiet because the street is a dead-end (no through traffic). A negative thing concerning the location is a disgusting red-lamp street close by.

Service is very friendly. Good buffet breakfast.
Rooms are nice and clean and rather small with a modern and clean small bathroom (if there is a bathroom in the room) but the carpets in all areas need cleaning or replacing. If it wasn't for the carpets, everything would look really nice and rather new.

One has to be careful when booking a room: some rooms are without private toilets. I had booked two rooms for us and one of them involuntarily without a private bathroom. This was not clearly marked on the website I had used (of course I was also not expecting a 3-star hotel to run rooms without toilets). So I ended paying a bit extra for a room with conveniences.

Considering the price I found it a good choice (after the trouble with the bathroom was solved) and would stay there again.

Convenient, affordable hotel located close to the station and the centre of the city. Too bad you have to pass through the sleazy red light district if you want to get out. Very friendly staff that spoke good english. Free wireless internet in every room. Spacious rooms, no noise at night to keep you awake, but the bed and pillows weren't all that comfortable. Car parking available but reserve in advance. Great breakfast but the breakfast staff wasn't always quick to refill.

Stayed a night during a stop over in Frankfurt. Location was great, but finding the hotel took me a little longer as it was (like other mentioned) tucked away in the alley way, where the entrance to the alley way is found between the stores fronts. So it is less than 10 minute walk from the train station.

Likes:
Location from the train station
Affordable
Wifi

Dislikes:
A little sketchy in the red light district
Shared washroom for my accommadation, so one toilet for the floor and thus everyone had a key, which can be used to unlock the door while inside doing your business.

Location: Hotel Adler is conveniently located next to Frankfurt Main Station - although it was hard to find because it's tucked away in an alley. (it's actually right across from Levis Hotel)
Restaurants: There aren't too many around the area, probably have to search around the Main Station to find them.
Breakfast: included but not all that tasty
Service: Front desk is helpful and sincere. They let us store our bags in the lobby on the day we checked out. (The lobby is located on second floor, which is quite strange)
Given the price of the hotel, I would recommend it to people who are traveling on a budget and don't mind the small rooms and small beds. It's close to the red light district, but no harms there as long as you don't walk through the area too late at night.