When I got my 3rd generation 64GB iPod touch it was my first Apple touch device and I used it daily, sometimes for several hours. It is a very versatile gadget and it's so much fun to use.
Then I got an iPad.
I used the iPod touch for browsing the internet, checking iTunes for new music, playing some RPGs, and fooling around with some music apps. The iPad does everything better for me. I now use the iPad to do all the stuff I formerly used the iPod for and furthermore handle most of my eMail and social network correspondence, online banking, eBook reading, and work related preparations with it. It is that much more comfortable to use. Oh, and I'm writing this on my iPad. My iPod touch has become a basic music and audiobook player. The 4g could have changed that to a small degree if it had a 3G option. Portable internet is just great.
In essence, think about what exactly you want to use it for. I now could easily live without my iPod touch. The iPad is a keeper.