I have one of the silicone cases and I just remove it before I put it on. But I am pondering getting a Skinit skin and wonder if it would add too much thickness. Maybe its time to break out the dremel...
BTW, I scored one of the deals from the AT&T store where you buy the Infuse 4G car dock for $17+, and get the desktop dock for $.50 (yes, the guy at the counter was as shocked as you are, if you have not heard of this deal yet). The docks fit, and you can tell that its made for the more squared-off Infuse, but for the price, its a lovely compromise for me versus paying nearly $80 for both official E4GT docks elsewhere.