>>1169482YZF450X with Yeti 120 on it.
Been on the ST, LT, and SX Timbersleds years ago, haven't been on one of the newer ones though.
I'd also like to throw a leg over a CMX kit sometime.
They're fun, a different kind of riding style though. Being a moto and sled rider, the snowbikes still take some getting used to - they don't ride exactly like a bike, and they're not really like a sled either.
They suck if you're the only snowbike rider in a group of sleds, and they suck if you're the sled rider in a group of bikes.
As far as >cheap ... got some bad news for you. The kit itself is $2-3k, plus the cost of the bike.
While hte bike stays a little cleaner, you're on the engine a lot harder than in dirt-mode, so you have to stay on top of oil changes and other maintenance. You'll want at minimum a 450; the 500+ bigbores are a lot more fun (especially at altitude).