The Slider comes in white gloss or black matte, and it fits the iPhone 3G so snugly, you might mistake it for the actual case if it had an Apple logo. It's got sleek style to spare.
You get access to all the controls with the case on, but if you have trouble fitting a dock accessory into the iPhone's dock port, the whole bottom 20 percent or so of the Slider case, well, slides right off. The first few times you perform this little maneuver it may seem tough to pry the two pieces of the case apart, since they fit together so darn well, but it gets easier after a few repetitions.
Our white gloss case seemed to pick up a little pocket lint, though, especially around the recessed Incase logo. Plus, at $35 it's on the high-roller side.

Links:
[1] http://www.maclife.com/user/sochs
[2] http://www.maclife.com/article/reviews/incase_slider_case_iphone_3g_0
[3] http://www.maclife.com/iphone3gcases
[4] http://www.maclife.com/article/reviews/agent_18_ecoshield_iphone_3g
[5] http://www.maclife.com/article/reviews/scosche_kickback
[6] http://goincase.com/products/detail/slider-case-cl59056