Although it's come a long way since its early days, I was never a huge fan of NetworkManager in earlier Ubuntu releases. It's always seemed kind of ugly on a compiz-enabled desktop, and even in Jaunty, I found myself resorting occasionally to wicd or manual connections because NM had issues with some of the wireless networks I need to connect to (in particular, it never liked WPA-enterprise security very much).
While I haven't been using Ubuntu 9.10 on my laptop long enough to say anything with certainty, the technical failings suffered by NM in earlier releases seem to have disappeared under Karmic. I have yet to experience a single dropped connection, and the "Create New Wireless Network" feature, which simplifies the creation of ad-hoc networks, even appears to work as expected with my Broadcom hardware, which is a first (although it may have more to do with fixes to the b43 driver than NetworkManager).
On the non-technical front, NM in Karmic has received a major facelift, with much more elegant icons and animations. Here's a look at the new art in action:
By my standards, this is a major aesthetic improvement over the clunky and unclean icons of the original NetworkManager. The animation is also much more graceful.
On the downside, the new animation doesn't indicate how far the connection attempt has progressed--the old one distinguished between the stages of authentication, association and acquiring an address--but that's only something geeks will care about. There's also no longer a pop-up message when the connection is complete, but that's not a big deal.
Along with other updates to Ubuntu's look in Karmic, the changes to NetworkManager reflect a solid and successful effort to meet and surpass the interface enhancements of proprietary operating systems, demonstrating that software can be Free and good-looking at the same time.