Wow! I just came accross this posting... A part of myself feel sorry for those that reported bad experiences here but I have to correct things for the record and if somebody read this again later on...
I need to say that the gay nightlife is not that bad in Rome. Of course it is not Amsterdam or NYC but it is also definitively cheaper than those cities. I have never paid 25 euros, the most was probably 10 euros. You can avoid the cover (or get it reduced very much) by calling a cell phone number to get "on the list", even if you don't know anybody. They usually distribute flyers the night before in other clubs with the phone number or you can check in the monthly magazine distributed for free. Drinks are cheap, between 3-5 euros. Expect to pay the same for a bottle of water, a beer or a high alcohol content drink. There are only 3 good places that are open all nights, plus 1 different venue open only on thursday, friday and saturday. The Qube (a.k.a. Muccassassina) has been up for many years but on thursday and saturday it depends of the season. There are also 2 leather bars. During the summer, there is the "Gay Village" set-up which offer, for a few dollars cover charge, a gym, different disco floors, cheap drinks, a few stores and a bookstore. It is very popular and attract several hundred of visitors every night from the end of june to september.
The Coming Out is a pub and is popular up to midnight, than people go out to clubs. It is a good place to meet up and ask locals where is the night. It is located on Via San Giovanni in Laterano, where you can see the colosseum. It has a big gay flag painted on the door and you cannot miss it.
I am canadian but I have been living in Italy for several years; I am surprised specifically of jmscsc comments. I would never recommend Rome as the gay mecca but I think it has definitely something to offer that will be a very nice experience. We also have a leather bar and various saunas. In contrast with North America, all clubs will be going until after 5 am. We also have a gay beach organized by the city of Rome in Ostia which is very popular, specially on sundays where people (several hundreds) gather after the clubs. It is in Ostia (settimo cielo) and cannot be missed, it has several large rainbow flags on the 300 meters length of the beach.
There's definitely a nightlife, without doubt if you are here during the summer and not living here for several months, you just need to get organized.