Never had any drama with any of the brand-name chains. While there might be better/better value product out there, I have no doubt that any of the brand name chains will do the job beautifully.
Actually some of my bikes run the cheap and nasty Bizz-branded chains from that guy who advertises tyre & chain deals in Just Bikes (Aardvark Trading?!?), and they've caused me absolutely no drama (despite my initial nervousness!). They even seem to last about as well as the brand-name non-O-ring chains. That nervousness of mine means that I only put them on the lower powered bikes, but even the 428 version on the YZ125C is holding up great.
I did get one cheap o-ring from the same bloke and I never used it - straight out of the packet, it had loose and tight spots and generally failed to fill me with confidence.
The whole "O-ring chains suck too much power" is a crock of poop, as far as I can tell. Given the weight difference and increased friction as a percentage of what it takes to make a dirt bike move foward, you'd be looking a something like 0.05% loss - and anyone who can honestly say that they can feel even 1% power loss on a dirt bike is dreaming.
And remember that in a MX racing situation, most bikes are able to spin the rear wheel at will - meaning that you've got 'too much' power anyhow and losing a bit doesn't hurt.