I know that I just posted on my new Windows Mobile 6 device, but I had been using it for a few months. Another reason that I was glad about choosing the Blackjack was that a WM6.1 upgrade is supposed to happen for this device (and others carriers will not be so nice).
The typically spoken list of WM6.1 features is small. The first big one is the built-in support for System Center Mobile Device Manager. The second is UI and experience enhancements. My first stance on this was "that sounds nice" but I wasn't dying for it. If you go looking for an updated list, it's actually quite long. The user really wins with this release. For a video show of the highlights, click here.
Last week, corporate gave me a chance to upgrade to WM 6.1 and I jumped all over it. My first reason was for the look of new home screen. Actually, it was my biggest reason since I hadn't held a WM 6.1 device yet. (My wife asked me if I did this because of the new color, going from black to a red device.) A few minutes with this device, and it really has a much bigger set of improvements than I had realized.
Why care about the WM 6.1 home screen
Other Features That Are Important to Me
So, if you're fortunate enough to get WM 6.1 on your device, I'd say "go for it". You'll get the best features from WM5, WM6, plus some cool ones like what I mention above.