Now that United.Colo is switching over to Williams (not adding, SWITCHING unless you buy more than 20Mbit) I'm concerned about the latency of my boxes. I know Williams used to have Cogent-like pings (ugh) but I'd like your opinions on their recent latency if your packets regulary go over Williams lines to your servers.

WCG is much better than it was and seems to be continually improving.

Adding a different transit provider won't solve any of UCG's internal networking problems, though.

Williams is not that bad of a network but I would never use them as my only network. If you run BGP with them they are good. They have some decent peering with a few companies and with them being as cheap as they are. Works out well in that case.