Mark,
I've been using sand for well over 18 months now. Paul is correct, you must control your temps on the way up when using sand, if you do this, you won't have any problems at all.
Some say that radiant heat from the sand can cause higher temps on the lower grate, I have not found that to be a problem. I usually am cooking butts on the lower grate and they can handle a little higher temp any way, but it's not that much higher, if at all.
Clean up is easy too, by the way.