IMO test them for yourself and juste do a battery pull after done. i like the iringrevolution the best, or the bottum scroller, there are plenty to test.
For me it was the iPhone 3G theme from Themes4BB.com.. i think i kept it the longest.... all these very creative themes have to many bugs and slow down my phone way too much
I loved iring revolution, but it seemed to slow my phone down, and iring leopard has the 2 bluetooth icons that didn't bother me at first because i didn't have a bluetooth i was using. i just installed linux v6 and i'm liking it. it's nice and simple and looks great. but yeah, just install and see how you like them. all a personal choice and with the way each phone seems to work differently with software (ie. os leaks: some have no probs, others find bugs every which way they turn).
Custom Dark is running great on my Storm. Really slick idea on the Storm. Lots of great thought given to each area. Tons and tons of backgrounds to play with. Worth a look, it's free!
The message centric today L (leather) by Jubz is easily the smoothest running. He made is simple, and functional and i've noticed ZERO lag/memory leak with it. I've tried pretty much everything, but this bad boy is easily the best considering everything is being developed on a leaked,unofficial, beta version of Plazmic. (note: i found considerable memory leak with the Custom Dark - great design, but so 'busy' that you are bound to have reduced app memory)
