I've LOVED it. The majority of the ultra runners are kooky/cool/fun and interesting people. I was pleasantly surprised to find people of ALL body types and ages finishing 50 and 100 mile races as well. Here is a great article about Mirna Valerio, a 250lb ultrarunner:

http://www.runnersworld.com/runners-stories/ultra

Harrier Hash is another very fun running club to check out.

I would say a good way to get started is to check out volunteering at some races, see if you like the vibe. There are some aid stations at Western States every year that are a lot of fun.

The PCTR races are fun and low key and a good way to start out in the sport. My best advice to to stay within yourself and have fun with the training and the races. Listen to your body and if it needs a break give it a break, build up to ultra miles slowly, your body will think you for it.