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Sub 
I'm shifting to a two split, upper vs lower body thing at 3-4 workouts per week. (I have been doing 3-splits chest/back/legs for ages and want to try something new for a while.)
I did legs yesterday and can't imagine doing heavy ("heavy" for me, not powerlifter heavy) lifting again so soon after. I'm thinking of alternating my lower body days as weights one session and bw the other.
Does anyone have any experience with that idea?
I've experimented with something similar CD. I'd alternate weighted and unweighted workouts. I've also alternated weighted and unweighted weeks. It's somewhat along the lines of pendulum training:
http://www.t-nation.com/free_online_article/sports_body_training_performance/pendulum_training
I had some success as long as I slowed my attempted gains down to baby steps. At the end of the day, I'm reminded of the old zen proverb of "the hunter that chases two rabbits catches neither one". I've gone through years of constant variation and almost paralysis by analysis where I was constantly tweaking routines trying to accomplish everything. I've always had my greatest results when I focused solely on a single thing: maximal strength, strength endurance, gymnastics strength, or whatever. Whenever I tried "focussing" on more than one thing, progress would grind to a near halt after a brief period of introductory gains. Nature favors the specialist.
I know I'm late to the party on this thread, but here's a few of my thoughts that haven't really been touched on yet...
I look at BW training the same as I do KB training or DB training or sandbag workouts. While the tool and/or exercises being used are definitely a part of the reason why certain protocols are effective, what's more responsible for the results are the principles being employed in the first place.
By that, I mean if you think BW squats are better than barbell squats, why is that? Simply saying b/c they're done with bodyweight isn't a good enough answer.
I can do barbell squats for 4 sets x 6 reps with a progressively heavier weight and get strong as hell. However, if I did BW squats for 4 x 6, it would be largely useless b/c the volume wouldn't be there.
Conversely, if the notion that BW squats for high reps are a good idea, what constitutes "high reps"? If you do 300 BW squats but I do 200 squats with an empty bar on my back and person #3 can do 100 squats with 135lbs on his back, aside from the total volume being done, is there really a difference? Not really - the principle being employed in the same.
Tools create fanboys. Principles create results.
Figure out which principles will lead to the results you desire and proceed from there.