We (http://www.fool.com) are currently using Sentry with a few Django sites, a few Wordpress sites and (very sparingly) with some C# code. There have been a few hiccups here and there with the UI, but we have been extremely happy with the service so far.

As a side note, we also have a legacy internal log error application that we also use, but it is nice to not have to deal with any of that infrastructure :).