The question now is - how difficult is it to replace a regular hd in this generation of Macbooks? In my 3yr old laptop it was a manageable, although a bit stressful, to pull out the hd and replace with an SSD.
I can't speak for the newer, non-user-replaceable-battery models, but I can't imagine they made it harder to replace the HDD.
Start imagining. You need a mini-torx screwdriver to get the hdd out, once you get the cover off (8 phillips screws).
Not the end of the world, but not too many people have a T8 sitting around. I didn't.
In other words, it's still orders of magnitude better than replacing the HD in, say, an iBook.