Call us crazy, but we're going to try it - a leaked ROM update for the Blackjack. Looks like it indcludes HSDPA too, so it's pretty hard to turn down. A quick search should yield it for you fairly easily. Otherwise, the mere existence of this bugger should mean the official one may come sooner than we feared.
if you're a BlackJack owner and don't want to wait until the official ROM update for WM6 on the BlackJack (expected Q3-ish of this year), it's floating around the web somewhere (hint, AT&T Samsung forums). Get it while it's hot - because I'm sure it'll be taken down soon!