I've never had a laptop battery that I haven't replaced in a year, which reminds me, I need to order one. (I traveled a lot though until recently, maybe that will change.) I've never seen a laptop's battery life claim that was anywhere close to reality either. If Apple (or any OEM) says 8 hours for 5 years, it means 4-5 hours at first sloping down to about one hour in a year. There's sort of a nuclear arms race there that forces all OEMs to lie similarly, because if they didn't the other guy would sell better, though I guess if one were in a position to break the standoff, it might be Apple.

However if I liked the laptop enough, and if I were able to find out via the internet that the battery held up in the real world for a couple years, and really got good life, and was replaceable with a trip to the Apple store, then yeah, it wouldn't be a huge deterrent.

Still, overall I'd consider a user-replaceable battery similar to cruise control on a car. Not 100% necessary, but really nice when it's usable and would I really want to buy one without it?