Based on what others have said I think I had a great first Bikram class. The instructor was completely ok with me taking several breaks (to avoid blacking out). And i felt physically better for the experience. I should also say the studio is excellent; very clean, great floors, glass walls and mirrors!
The mental experience is surprising. All the Yoga classes I've done in past at other studios have always had a strong emphasis on breathing and self awareness. Bikram is mentally tough. It's not about giving your mind pause to focus on the poses and how you feel. You are being constantly pushed with instruction and feedback. and I mean constantly (exception being Sivasana). It's a very go go go! Push push push! Experience. So if that's not your thing then you might want to try a one off class OR try another style.