It's all about your particular requirements.

If I get a tablet I need to be able to carry it one-handed (so 7" screen), to have the internet accessible while I am out and about (hence built-in 3G) while using GPS (hence that built-in as well). And the software I like is free on Android. The rest (email, web browsing, Facebook etc at home or work) can all be done on any tablet.

So in my case the best combination I've seen to date comes together in the Galaxy Tab.

My son purchased an Optus MyTab and is happy with it - it fits all the criteria but has a few limitations including very poor screen legibility in direct sunlight that make it not as suitable for my particular usage.