I have more energy, I feel more productive, I feel stronger and therefore more confident. I also have much more flexibility (to a shocking amount!), and my sciatic nerve has stopped bothering me (it used to get gradually worse throughout the day). I can feel muscles in my abdomen and arms! (and by that I mean I can feel them on the inside, not I can touch them with my hand and feel them) and best of all, last period I had NO CRAMPS. ZERO. Except for the obvious, I couldn't even tell I was menstruating! This after the month before when I had the worst I'd had in a year, probably. For me, working out my core muscles and drinking lots of water is just magic.
an odd side effect is that I'm more aware of the effect different foods/drinks have on my body. I love coffee, as you all know, but I can't stand to have it (or any sugary drink) sooner than 5 hours before or an hour after a workout. And if I don't have enough protein I feel dreadful after a workout (yay for odwalla & luna bars!). Also, I crave veggies more and greasy foods less -- even one fry will make me feel crappy, as I discovered the other day when Ben gave me one of his. It has no effect on my love of Mexican food though ;-)