TF300t, got it yesterday, still trying out different layouts but this is the one i'm currently using.
Well, so far, it's okay i've been having some (keyword some) issues that i'm not entirely sure of. My main problem with the device has got to be the browser, on Chrome beta I get lag, it'll occasionally freeze, which bugs me, (also happens on stock browser) but it's consistently snappy out of the browser, other than that it seems like it takes a little too long to load a webpage. (compared to my Android 4.0.3 phone on wifi) Please do note that the browser issue is also happening on my mothers tablet too. (Same one, bought same time) The battery life is AMAZING-ZING
Have you tried another web browser? Dolphin? Opera Mobile? By laggy do you mean scrolling is slow? You have a Quad-Core Processor on a very hardware-accelerated operating system. Should be no lag, especially in terms of scrolling/zooming and general usage. You know, that stuff iOS is excellent at because it puts it at the top priority for the processor.
I have not, but i probably should. I'm also quite tempted to root it (boy do i miss being able to view/edit the file system) Trying Opera now.
Root it and try some custom ROMs. That's what Android is about - well, at least to me it is. The customization - ROMs, themes, launchers, etc make Android Android.
The TF300t is rather new on the market. Give it a month, its similar enough to the Prime that they should start showing up pretty soon.
Talk to ValleyForge about rooting. Also would you mind posting your wallpaper from your first screenshot