I'm hoping to thru-hike the PCT in 2008, and just went through this thought process. I like my Kodak V570 a lot because of the built-in wide angle lense and on-camera stitching software, but I didn't want to rely on mailing batteries back home to recharge or hassling with a charger in my bounce bucket, so I looked for something decent that takes AA batteries (I'll use lithiums) and isn't too heavy or bulky.
Measured weight for my Pentax Optio M20 with NiMH rechargeable batteries and an SD card is 6.9 oz (195g), that includes the little carry strap. With no batteries but the SD card left it it's 4.7 oz (134g).
My notes say that a pair of lithium AA's weighs 0.9 oz (25g), so with those the total weight should be 5.6 oz (159g).
No optical viewfinder unfortunately, but I think the reviews said it nevertheless does pretty well on battery useage.
I haven't yet used this often enough to comment on how well it works on a long backpacking trip, but I think it's likely it will work out fine. And a really big (2 GB) SD card isn't too expensive these days, which limits how often I'll have to mail the SD card home, if at all. It seems like I read in too many trip logs how a camera memory card mailed home fails to make it for whatever reason!