I FOUND A WAY TO GET MULTITASKING/WALLPAPERS WORKING SMOOTHLY ON A 3G!
Some of you may have already figured this out, but I thought I'd say it anyway. After trying the Beta 1 jailbreak (worked, but MT/HW slowed it WAY down) and Beta 2 (still no MT/HW), I played around with it and found a very usable solution. Put only 4 icons/folders per homescreen. It sounds so simple, but it works nearly perfectly. If you can live with either flipping through many pages of apps or having lots of folders, this should suit you well.
Seriously.
BONUS: This strategy is especially attractive if you have a wallpaper with a centered image, like the Earth wallpaper that's built in.
Edit: BTW, you need to be running jailbroken Beta 1 to do any of this. (redsn0w 0.9.5)