I have been running them for years,and i can tell you anyone running these setups and having trouble either doesnt have it setup right or the jetting is off.
I got one on my trail bike,and i have one on my ported bike.On the trail bike i run a 33pwk and an airbox,and the other im running a 35 or 36(pwk) and a clamp on filter. The bike with the bigger carb is ported and t5's. They are by far the single best investment i have made for both quads. Jetting is quick and easy--and cheaper/it makes more room/thumb throttle is easier,i just think for trail riding and play riding it is an awesome set-up. 2 carbs work just fine,but i just really like the single carb way better.
For dune or drag though i would stick with 2 carbs.
I swear by these kits,and its always the first thing i buy for a banshee
Remember this is all a matter of opinion though.