I've been considering adding a Quaife to my 03 SL55 which has a few power mods, and wondering if the LSD will affect my rear tire wear?

only if you drop it while listening to jimmy hendricks

Actually it should help them wear more evenly, if you are aligned that is.

Seems like LSD will help traction and not lead to increased tire wear unless camber and toe are out of spec already

Ha!

Pretty funny.

yes, an lsd will even the tire wear as opposed to an open diff where one tire gets to do all the work and that brake pad wears also faster as the edc tries to emulate an lsd by braking the spinning wheel...
holly run-on sentence

I did a Quaife recently in my SL. Rear tire wear is still apparent due to my right foot, but it looks to be perfectly even now.

Very happy with the Quaife upgrade, it really facilitates traction on the street.