Susan -
I'm really sorry to hear about your pnuemonia. I didn't suffer that, but I was down in Louisianna after hurricane Katrina w/ the Red Cross and I came back, not as well as I would like. It took me a month to recover, and another month to get back to the intensity I could do before. I wish you a speedy recovery!
Now, I've done the beginner and intermediate sections of Bryan Kest's Power yoga. They are very intense workouts, but in a different way. I'm not used to twisting and holding lunges the way we do in those and I tell you that I get more sore in the hams and glutes from the yoga than I do from even GS Legs - amazing, eh?
I'm going to continue and make sure I add yoga (either Bryan Rodney Yee's yoga for athletes or the yoga class at my gym) at least 3 times a week - preferable 4. I'll let you know how it goes.