There are several good articles and posts, and even a book, about on this at backpackinglight.com (some may require a subscription). They also have a free podcast series about a couple that hiked and packrafted all the way up the Pacific Coast, through Canada and Alaska, this past year.

Looks like everyone who's doing it seriously is using the Alpacka. I have a Sevylor and will agree with everyone else on them being fine for some fun paddling around a lake, but probably not suited for serious use.