I've been travelling for business reasons many times in the last many years to Hannover, and from all local hotels I've been in, the Courtyard is by far the best.
The staff is correct. The food in "Julian's bar" is pretty decent, the menu a bit more restricted that in the restaurant but the atmosphere much "cozier". Breakfast is good and there are always free newspapers at the morning. The rooms are spacious, the beds very good and the sight from the rooms heading the lake is, without doubt, the best from any hotel in Hannover.
Last year they refurbished the lobby area and put TV flat screens on the rooms.
Jus two minor issues:
1) The rooms still need some "freshen up", specially the bathrooms are getting a bit old
2) If you are travelling with public transport, there's quite a walk (10-15 min) to the nearest subway station
Tip for runners: Though it's pretty straight forward, the maschsee 6km round on a hardened dirt path, must be the best running place in town and any day at any time there is always people running around, so no need to visit the fitness room in the hotel ;-)
Tip #2: If you want rest, please AVOID at any price the period around the Maschseefesten (somewhere in August), as it can get VERY loud in and outside the hotel

Adequate hotel with average rooms, and a breakfast that randomly varies from poor to average.
Staff are very friendly though and always seem happy to help.

nice location at the lake but far from city center, not a walking distance and nothing to do around, just walk around the lake.
needs some renovation rooms are not Marriott standard at all, very very simple, cheap features.
better hotels in the city.
if you have a car location pretty good, parking expensive though
great gym in the opposite end of lake, with great spa. pools etc.

The hotel and the room is quite standard and no complain about it. The location of the hotel is next to a stadium, which could be disturbing when there's sport event going on. Unfortunately there was a soccer match being held in the stadium on the day that we arrived. The road to the hotel was blocked and we had difficulties driving directly to the hotel. Our room was facing the stadium, which we could hear the noises from there. But other than that, the location is OK. The city is within walking distance from the hotel.

Overall, we are satisfied with the stay in this hotel. The room was clean and considered spacious in the European standard.