I've owned eVLution 2s, a 3, and now I own a 4. The problems with the 1-3s were that they were using polycarbonate bodiesand it was simply ill suited for the designs used of the battery door, the loading door, and the body (if I remember correctly, they didn't thread bolts into nuts (like on a halo) but rather screws into polycarbonate-yuck).
The eVLution 4 is a great little loader: The shell has a durability at least as good as a rotor, if not as good as an original revvy (I have both). The feedneck is very robust, combine that with the pushpin teardown, and no battery door. Interestingly enough, unlike all of my previous Evlutions, this door hasn't started cracking apart, on it's own, on the shelf (like the other ones did). I can't say for certain but, it feels like it might be a different plastic than what they were using before (slightly softer?). It is the same design though.
Looking at the pics, I'd say this could be a real good loader. A super-robust feedneck, a body with a shell material similar to, or the same as the revvy/rotor, possible speedfeed options (rather than the homebrew stuff for the earlier models), a decent speed (I dunno about '18BPS' but, it's at least enough for any rec baller) breakbeam eyes and pushpin teardown. Aside from Aesthetics, what's not to like?
Personally what I find most appealing of the Evlution 4 is not going to be in the newest: the rear slung body. The older body style works amazing for Warp Feeds.
As for the feedneck, I don't think Viewloader made them to force us to sand them down (they fit fine in the 98C feednecks and even my warp feed, and I think (I'd have to check to be sure) that it fits in my Deadlywind no-rise feedneck. Viewloader/Kee probably did it for durability given that in generations 1-4, having the body of the loader offset to the rear allows for much more leverage to be applied against the neck of the loader. I'd blame the lack of fitment on some marker / feedneck designers making feednecks only capable of holding skinny little feednecks not much bigger than what was used in the halo (tell me those weren't designed to fail).