I thought long and hard about BlackRapid, but went with OP/TECH after reading too many horror stories about BlackRapid strap failing at one spot or another. The price differential doesn't hurt, either.
I haven't used/tried it too long, but I'm liking the OP/TECH a lot thus far. I'd been perfectly happy carrying my camera with wrist strap, but I've been having problems with my right wrist and having a comfortable neck strap is going to be nice.