How were you into muzzleloading before? If you're used to traditional sidelock rifles, those inlines are gonna leave you feelin' kinda funny. They handle like a modern boltaction, and if that's your bag, go for it. For what it's worth, inlines are not "new"; I've seen pictures of an inline flintlock, which would pretty well argue for 18th Century, maybe even the 17th. It's just not what we're used to seeing.
Also, for what it's worth, the inlines available today (some of 'em are even blister-packed. Really!), the quality seems to be pretty good, and they shoot satisfactorily and are safe, at least if you follow the rules. One negative note: a fellow was next to me at the range a while back...he was using an inline with saboted pistol bullets, and he was having a devil of a time ramming them home. Those puppies were TIGHT! I don't know if this is a universal condition or not.