1 mm is OK but if I see 2mm I adjust the spots that are out.

A good check for even tension is to tap the spokes with a plastic screwdriver handle. All the spokes on a side should sound close to the same and give a musical tone. If they just give a dead sounding thump then they are far too loose.

The front on a rim brake wheel should sound the same side to side. A few "keys" difference isn't a big deal but if you hear a full octave difference it's time to retension and retrue.

Here's a freeware piano note generator to get an idea of what I'm talking about....

http://www.freedownloadscenter.com/M...nic_Piano.html