The old 7700 wheels and the Ultegra equivalent have issues with spoke tension. If they are too loose they alway go out of true. I got rid of a pair for this reason. If you go too tight, you greatly risk breaking spokes and they are not a common item stocked at a LBS. i sold mine to a less aggresive and light friend...she has been happy so far. Ksyriums fall victim to this from what I have heard.
I would definitely go with a custom wheelset. They are often times less expensive and lighter, while being just as strong if not stronger. Boutique wheels are fine, I have owned a set of Heliums and love em...never had an issue with them, but for the money I paid, I could have bought 2 sets of custom wheels that were just as light.
That being said...if you score a set cheap, go for it. I have been lusting after a set of 404's or 303's for a long time now...yet I can't justify spending the money. I won't by carbon rimed wheels used...so they will stay on the wish list for me.
Enjoy those wheels...now quit fussing and ride that darn bike!!!