The stealership tried to tell me that "all LS650's need valve lash adjustment at 600 miles"  and wanted to charge me for inspection AND adjustment before they even looked at it. So I told them to forget it.

I did my own 600 mile check and found them to be within tolerance, but one was at the max so I adjusted it in by 0.001". Checking is a pain, adjusting is a piece of cake.  

However, I do think it is a good idea to do the whole 600 mile check, including the oil change, retorquing the head bolts, checking cables, etc. They don't call them thumpers for nothing and I was amazed how quickly things had loosened up.  It's your call, but I would not want to wait until the 5000 mile checkup to do all the required checks.

I got a little over 4,000 miles on mine, and have checked the valves three times (OK, I'm a little anal). Each time they've been within spec. That said, I'd still check 'em. As was said here already, checking them is a PIA, adjust them (if necessary) is a snap.