I'm first dan in usa karate, though I haven't been associated with them in years. I've been in Krav Maga for two years, testing into level III. It's an interesting style, ruthless, very street orientated - I was a bit annoyed by the sport aspect of Karate, and this style doesn't promote a sport too it. Only real life training and camaraderie.
American Kenpo gets a bad rep because a) there are so many bad teachers and b) students don't realize what the system is trying to teach. If you understand how the system is set up and how to utilize it, it is a very effective art for self defense and fighting. Much of the system is a study of motion and physical concepts. The people who buy these as actual self defense will get a rude awakening at some point (and likely give the rest of us a bad name). Those who learn the lessons hidden in the system will become excellent fighters.
Just started a really good BJJ school, and they also teach Muay Tai. The school is geared towards MMA style fighting, but its fun. Karate gets a bad rep cause of the sport aspect, but I have known some really good karate guys.
I've been training BJJ for about 3 years now and Kenpo only for a couple months. The kenpo is to help my pathetic standup but i love the jiu jitsu and the ground work :)