The hotel is of a good standard, what you would expect from a Mercure. However I had a very uncomfortable sleep. I wouldn't normally say this but my work colleague also had the same, so its worth mentioning. We were only there for one evening, however, so there was no chance to re-evaluate.
The hotel bar is very small and closes at 11pm, so after this there is no place to really convene and talk (we had a business meeting at 11 due to our late arrival to Erfurt) which we had to hold in the seats in front of the reception desk.
However if you are there for somewhere to sleep, then it is a good hotel.