I've been finding it quite beneficial to go different classes taught by different teachers. Finding commonalities between the classes help in realizing the fundamentals. If one teacher tells you to do something a certain way, you take it as a grain of salt. But if all the teachers tell you to do it, you do it. In addition, it's educational to see not only different styles of yoga but to also see different styles of teaching yoga. I find that I like teachers who talk concisely and calmly. No love here for teachers who excitedly share stories throughout practice - there are better times for that.
Though I encourage some promiscuity in the realm of yoga classes, it's best to keep it at a minimum and continue to attend that one class/style that you really connect to. It's like in any other relationship. It's good to have acquaintances who you learn and seek different perspectives from but you always need that close friend(s) who knows what's best for you.
Btw, been seeing A LOT of couples in the classes I've been going to. 4 couples last night. Is 2012 the year for couples yoga?