I'll definitely have to see if I can demo a Slash in the next year. I'm a little concerned about how the new single pivot arrangement affects pedaling performance though and the proprietary knock block headset arrangement is a little annoying. Other than these two questions / annoyances it seems pretty much a perfect spec.
Does anyone have a Yeti SB5.5c? Other than the price, this is probably at the top of my list due to the absolutely glowing reviews I've read about its balance of up and downhill performance. My three reservations are: Price, durability of the switch infinity link for North Shore winter riding, and if the rear 140mm of travel is progressive enough to keep me from bottoming out too often due to my 'bull in a china shop' riding style - or lack of style:(
Banshee also have a great rep for durability but 135 mm rear travel on the Prime seems just a little too short to me and they are a little on the heavy side. Ideally I'd like to keep my build around the 30ish lbs my current bike is.
I got the 5.5 in the summer. I've had a few issues with parts around the bike (for whatever reason), so I haven't had as much time on it as I'd like. No issues with the frame or the infinity link. I pulled it apart a week ago to clean and re-grease it and there was no noticeable signs of wear.
I haven't ridden the other bikes in your list, so it's a little hard for me to compare. Anyway, the Yeti is the best pedalling bike I have owned in a long time (Nomad, Ibis HD3, Knolly Endorphin, etc.). And it's been the best companion for long days and I would say it's the best all around bike I've ridden in a long time. Right now, I'm running a Push 11/6 on there and it feels like the rear end is calmed just a bit, which I really like. I was surprised how well it still pedalled with the coil. My only note or criticism is that bike feels very racey. If I'm out pushing it hard, the bike feels just awesome. But I find when I back off a bit, it can feel like the bike is riding me. Maybe I don't have the perfect set up yet though.
Last thing, I found it pretty hard to bottom the bike even with the stock Fox set up. Even the Push is very difficult to bottom. But if you're looking to plow down Ned's, then probably check out one of the bigger bikes on your list.