I bought the black razr at the same time a friend bought the silver. The key difference is the black razr comes with a backlight limit of 20 seconds as opposed to 60 seconds for the silver. I've kind of gotten used to it, but it's still annoying to buy the same phone with more limited functionality. This is fixable (as I found out thanks to some very helpful members of this forum) through seem edit, however. That's the only difference I've noticed between the phones.
Even with this limit, I love this phone and would take it over the silver (which I think looks great, btw).