Main problem with carbon is most companies make them too light or they're made in China where the process control is shit. Frames made in Taiwan that aren't stupid light are usually quite reliable, I've beaten the hell out of my bike for 6 years & counting and crashed it hard many times with no damage. Still, I consider it to be somewhat disposable and don't expect it to last 20+ years like a good steel or titanium bike.
As for titanium, there's not too many manufacturers I'd trust to be honest. Moots, Seven Cycles, old Ibis, older Merlins, and frames made by Sandvik for a number of companies are the good ones, most of the others are buyer beware and anything from China is junk. There's only a handful of mills producing high quality titanium tubing in bicycle sizes and welding it properly takes a lot more attention to detail than steel. Lots of manufacturers source the wrong tubing or mess up the welding so the frame often rides poorly or cracks apart prematurely. But when it's done right it rides better than anything else and lasts pretty much forever.
