Been running tubeless for ~3000 miles now, had a few punctures and only one where the sealant couldn't deal with it, this was where a small piece of flint got stuck in the hole and agitated the sealant and so wouldn't seal. By the time I got to it I'd lost most of the sealant so had to tube the tyre which was no more hassle than if I'd been running an inner tube (although was a little bit messier).
I'm running non-tubeless 38mm Schwalbe G-One tyres on non-tubeless Mavic Aksiums rims @ 45 psi front & back, and have not encountered any real problems doing so, think I must be one of the lucky ones!