I don't think it's all that great an idea, but there are other people on this board who are doing it. Go to www.lawschooldiscussion.org
and do a search from there to find the various threads where people are talking about it.
My take: you have to do significantly better for it to make any difference, and there's no guarantee that your score wouldn't be even lower, which never looks good. Second, you should try to find out when most of the people get off the waitlists at your schools. The June score will come out in late June/early July (I don't have the exact date), which may come after the time when your school has already released or accepted a number of waitlisters.
I can't imagine it helping all that much unless you're certain you can really bump up the score and get it in before it is too late. BUT, I know some others are doing it, so again, do some searching.
Best of luck.
EDIT: If you applied really late, you may also want to consider taking the June test and sitting out this cycle to reapply for fall '08. Your waitlists may have been acceptances (depending on your numbers) if you had applied earlier. If you decide to take this path, though, you should consider whether or not you want to wait until September instead of rushing to take the June test. At this point, you have nothing to lose by taking in June (except the money, time, and stress), but if you decide to wait, a rushed score in June may not be in your best interest.