To be honest, I think the current pricing for the next gen Intel SSDs (Intel 320 and Intel 510) are a bit crazy. I think what's happening is that limited stock being available is allowing importers to charge a hefty premium on these drives. Hopefully as more stock becomes available, the prices will come down.
RE the question of SATA 3 via PCI-E vs onboard SATA 3. Long answer... depends on the drive, the chipset on the motherboard, the number of PCI-E lanes the card has, the configuration of the PCI-E setup on the system, etc etc. Short answer? Performance will be very, very similar. Performance will however be slower than the fastest Native PCI-E SSDs (Like the Revo Drive's).
In terms of what SSD to go for, I would agree and say wait for the Vertex 3 (or another Sandforce 2000 series based drive). They are dominating performance wise, and are expected to be roughly the same price as the Intel.
Finally, RE SSD reliability - they are generally less reliable than Hard Drives, but more reliable than Graphics cards. As with any data storage solution, expect your data do disappear at any moment, and act accordingly - keep multiple backups in multiple locations.
Hope that helps!
PS: An SSD is probably the best upgrade most people can do for non-gaming performance - it really is mindblowing. Every time I demo for people opening every application on my Macbook Pro at the same time (It's got a 160gb Intel X25-M and a Sandybridge Core i7) they are completely blown away. And the fact that while it's opening all those applications, the system is still usable? Awesome. Say goodbye to those frustrating micro-pauses! Having an SSD means your system feels like it's a brand new, clean, fresh install with nothing except a browser even after using it for a year.
