I purchased the Williams 30x about four weeks ago and have a little over 600 miles on them... I bought the x's as a precaution, as I could have probably went with the 30s (me, 6'2 180), given the urban riding and plentiful potholes I do in Saint Louis.
While I would caution my recommendations based upon the short ownership period, I can firmly report that these are the smoothest feeling wheels I have ever owned (and I have owned a lot, at price-points that far exceed this bargain). They seem durable, but time will tell.
Also, as others have said, Keith Williams has great customer service.
Highly recommended.