It works fine with both the HP and Microsoft docks, as well as most of the third party docks that exist. Alcatel and T-Mobile recommend the one from Incipio.
The IDOL 4S has an oleophobic coating, so is much better than the experience you described with the Fierce XL. Incipio is the maker of most of the cases which T-Mobile seems to be offering. They are pretty good, overall.