With any of these triggers, you do get what you pay for in terms of reliability, whether it's the old V2's, new V4's, or any of the remakes: There's always gonna be a decent chance of things going kaput.
Story: I've had a set of PT-04's that have survived well; A week after getting them I decided to go shoot some skate photography with my mate. Well I get in to the locale, set up my flash, get off a good burst of shots, and then.. paphuut. It totally stops working. Why? I shall never know, but it was pretty much out of action. Gladly for me, I was just testing them out on a D80 body, and so whipped up the CLS in no time at all. When I got back and tried them out again they worked perfectly, never had a problem before or since.
The reliability would not be an issue if it didn't happen to be most likely to occur at moments and situations where it would take too long/be too much effort to make them work, and that's when your images start suffering for it; gladly in this case I had a reliable backup with me, but you can never be so sure.