The battery life is amazing..... Unless you are playing games. If you are playing games you get about one and a half hours worth of battery life, instead of 36 hrs music & 6 hrs video. The battery charges very fast, a full charge takes about 45 min. The only bad thing that I can think of about the battery is the fact that you have to send it in to Apple to get it replaced.
The built-in speakers are a great idea. While the speakers aren't really fit for music, they are perfect for the iPod sound effects & games. The earbud sound quality is crystal-clear, and they are small & lightweight on top of that. I really like the volume controls built into the left side of the iPod. It completely eliminates the need to turn your iPod on to adjust the volume.
I haven't personally used the iPod+Nike, but I have heard that it is a nice feature.
The UI (User Interface) is really nice, all of the animations are smooth & complete. The on-screen keyboard, while the keys are small, is highly effective. Though it does take a few minutes to get used to. (If you haven't texted on a QWERTY keyboard before)
While the wi-fi isn't G3, it is surprisingly faster than you would think. The web browser is really fun to use. While you wouldn't want to use it to log into accounts, (ex. Yahoo! email) it is great for anything else.
In my opinion, the iPod Touch is a handheld Mac.