I just got the case last night. While it does add some girth (a little more than a comparable Speck case for an iPhone) it still fits easily in my shirt pocket. It is a lot easier to use the phone with it on, however because I don't inadvertently press the buttons on the side like I did when it was "naked". It is great protection for the phone and easily removed in those times where you don't want the bulk of a case. There's my $.02...
I bought it and love it, it is a bit pricey, though its cheaper than a new phone, id recommend looking online first EX: Amazon for cheap but protective phone cases and if you dont find one you like, then you can always go back to the sprint store.