My group tried C&C and loved it, but we played it as a break from our usual 3.5 campaign and went back to that after. I'd have no prob running C&C.
Some folks seem to have a little difficulty accepting the "C&C is easy to use with materials from all other editions" (someone called it "false advertising" iirc?), but I can vouch for it, having used the 1E DMG, Basic monsters, and 3.5 DCC's all during our short run, and all "on the fly". Maybe it would help to state a little more clearly that the *C&C Players Handbook* is easily compatible with all other editions' non-phb materials. As C&C is really little more than a PHB with a few modules, I don't see why anyone would be worried about running characters from other editions with C&C support materials. But C&C bases almost everything off of Hit Dice and Challenge level. For instance, if you use a 3.5 monster, all you need is its HD to determine its attack bonus, saving throws, and skills. If you use a spell or trap all you need is the relative level of the weilder or setter or caster or whatever, and there's your challenge rating to apply to your SIEGE check.
So the difference is instead of doing a technical "conversion" you're really for the most part omitting stuff that doesn't apply. Pretty simple.
That said, I've found a "happy place" with 3.5 by eliminating some things (AoO's anyone?) and modifying some other things (xp, 10th level "cap" instead of 20th) and don't really need C&C anymore, but I would still recommend it. Also looking at Ry's 6th lvl epic stuff, pretty cool!
I think C&C would become a more viable option for a lot of gamers if it became a more "complete" system, with an extensive DM's guide and MM's. There's already a Monsters and Treasures book, but it is oddly different in tone from the PHB, as if the writer of PHB were a huge 1E fan and the writer of the M&T book were more of a 2E fan. They just done mesh well, which is why I think a lot of folks prefer to dig out the stuff from other editions.