I first reviewed this hotel in July 2006, based on a very good first impression when my family and I booked an apartment there.
Most of what I wrote then still holds true -- the apartments in the hotel are definitely superior to the regular rooms, and a bargain in the center of Graz if you need the space.
However, since I wrote that review, I have been back to Gollner three times. Two out of those three times, I have had major problems getting them to honor my booking. I must therefore revise my original rating.
In December 2006, I used booking.com to reserve an apartment between Christmas and New Year's. On arrival, I gave them my booking confirmation, and they gave us the key. We went up to what we thought was an apartment, to discover it was just a regular business room. Back down to reception, where I pointed out I had reserved an apartment. They informed me there was no apartment available for all four nights of our reservation. We didn't have anywhere else to stay, so we had to take a regular room, which was very inconvenient. They also did not want to give us a lower price, complaining that the rate I had for the apartment from booking.com was already lower than their regular room rate. No one ever offered an explanation or much of an apology, and booking.com was not able to do anything about the situation.
In July 2008, we returned to Gollner, booking an apartment through ratestogo.com, because I hadn't had any problems using them before. As we walked into the lobby, I recognized the desk clerk as being the same person on the desk in December 2006, and immediately had a bad feeling. Sure enough, he gave me a key without saying anything, but I immediately recognized by the room number that it was not for an apartment. I pointed out that our reservation was for an apartment. He already had a copy of the booking behind the desk, and he pretended to study it closely, even though it said "APARTMENT" in bold letters, then said there was no apartment available. I went ballistic, and pointed out this was the second time this had happened.
After some time, he finally said we could get an apartment the next day, and again since we had nowhere else to go, we had to take the regular room for the night. Again, I never got any real explanation or apology.
I think it's safe to bet that the hotel holds low rate internet bookings only as long as no one else shows up ready to pay full price. So, I strongly advise anyone not booking directly with the hotel to be sure to confirm your reservation directly with the hotel, ideally via e-mail so you get it in writing. Still, don't be surprised if you show up and they don't give you what you booked.
I will not be returning.