Being a mechanic at a trail centre I see and work on a hell of a lot of tubeless wheels and have laced quite a few rims up.
I personally don't run tubeless, I very, very rarely get punctures and I ain't seriously fussed on the weight of my bike so I spend my money on other things.
Although the Stan's No Tubes option works well using their own rims. I've seated non tubeless tyres on all three rim options with ease. Mainly Maxxis tyres using sealant.
Also using the Stan's tubeless rim tape on non Stan's rims works as long as the inner wall of the rim is shallow, and again, using sealant.
As for valves, Stan's again, work for me every time.
I work with a few guys that run Flow rims on Maxxis non tubeless tyres front and rear. We do a lot of riding (trail centre stuff, natural stuff and even DH runs) and I can't remember them ever having a problem with this set up.