Most launchers I've used don't change the whole UI of everything, just gives you free reign to do what you want. Check into LauncherPro(plus), ADW, GoLauncher, they're all great. LauncherPro is my favorite for the widgets in the plus version mostly, +the dev is currently working on a rewrite (slowly
) that should really change things and give it a big advantage over it's competitors. ADW (ADWEX has more features) gives you themes and is great as well. GoLauncher, the newest of the 3 has some really great devs behind it who keep improving it drastically (I'd say it's probably the fastest currently - though the difference between the 3 is minimal).
Alternatively, maybe Dexter's Blur version of 2.2 for XT720 keeps the buttons you want? (I think it does but haven't actually put either that or the stock 2.2. on yet, so I don't know).