Our stay in Agra got off to a bad start, having arranged for the hotel to send a taxi to collect us from the train station it failed to appear. When we called to ask what where the taxi was we were told none had been booked and it would cost us 3 times what we had preciously agreed. Needless to say, we used the pre-paid taxi rank instead and ended up paying half what the hotel had originally said they would charge.
Once in the hotel, the staff seem to be constantly looking for tips which became very annoying very quickly.
On our last evening and day there, there was no hot water.
Further afield in Agra, I recommend avoiding the TSR restaurant, I don't think it is a co-incidence that my wife and I had (our only) two days of severe diarrhea immediately after eating there.
In terms of things to do in Agra, we were only there for a few days and obviously the Taj Mahal was the main attraction. I'd recommend taking a trip to what is locally referred to as the "baby taj" and to view the taj itself from across the river at sunset if you have time.
I'd also recommend a trip out to Fathepur Sikri, we did this on the day of our departure from Agra so we only had a half day there but it was well worth the effort to squeeze it in.