Klaus.. you've made some really good points there. My working assumption with the U2 was that 'it's done when its done (properly)', and thus would be better than the L4/L5.
I'm actually looking at an L5 right now (shocking ain't it? /ubbthreads/images/graemlins/faint.gif), it could be bored out to accomodate the 18650s I like.
Basically, I regard the situation as a compromise, with rechargeables you take a performance hit but you do get the awesomely long runtimes - at 800mA, I'm looking at easily 2 hours on 1600mAH. Of course, not having level 6 is really no fun. 6 IS a heck of a lot brighter. I'd say it's the difference between 70 and 100 lumens on mine.
For those who need level 6, I guess, it's back to primary cells again. I just wish I didn't have to make this compromise on what, in my eyes, is THE light that refuses to compromise (or should refuse to /ubbthreads/images/graemlins/icon23.gif)
The reason I won't be trading down to a L5, much as I love the body style (the C2 was a big hit with me) and the ability to run full power on lithium ion is that I still value the multiple levels and the bezel down clip.
It would be great if we could get a few words from the Photon King himself on the subject, even if it is "It looks like you'll have to live with it". Do you think it would be wise to bring this up with him?