On the brightness question, I'll add my two cents. The Ultra Edge will make the color brighter, but it also sort of lightens it a little. It won't make a Guardian Blue into an Arctic or anything extreme like that, but it will seem a little lighter. It will also look, as everyone else has said, much fuller and even. In that regard, it will give you a blade much like what you see in the Prequels, or even ROTJ. The Mid Grade or Heavy Grade Blades on the other hand, give you a little more true color, but are less even and more 'shimmery' giving you a look something like the lightsabers in ANH and ESB before the Special Edition 'improvements' on Special Effects. It's really all a matter of preference.
Also, I gotta side with Duff on Durability. I always recommend buying a Heavy Grade no matter if you go Ultra Edge or not, just because it can survive most anything short of a nuclear holocaust.
Even if you don't intend to duel heavily, everyone gets carried away sometimes, friends might not have as much restraint as you, and of course, occasionally one hits a really really hard object by accident, and in those instances it is just awesome to have that extra strength in the blade to handle whatever comes your way.
