I wouldn't recommend to do any "fancy" stuff too soon, that includes overclocking and flashing to leaked 1.2 firmware.

Instead you should take your time to configure your phone, import/add your contacs, take a look at your browser and add bookmarks, setting up your widgets/shortcuts on the desktops.
After that, I'd take a look at the Application Manager and add Extras Testing, maybe even Extras-Devel to your catalogues. Right then install some applications I guess - there are some almost mandatory tools at least for me: Simple Brightness Applet to change display brightness on the fly or 2G/3G selector to quickly disable 3G when not needed. Download some themes (there are some really nice ones out there, take a look at the forums) and check for other wallpapers.

If the tablet runs fine for you - then I wouldn't see a reason to overclock other than pure curiosity. I for one overclocked to 800 MHz and while it IS faster, I am not sure if I *really* need this extra power.