• The wifi network list is unsorted (rather than obviously being sorted by signal strength).
• The wifi network list uses an animated progress bar.  This may look cool in screencasts, but when there are >20 networks in range, pulling up the list brings my computer to a crawl (due to 20 animated progress bars).
• The wifi network list is only accessible by clicking on the nm-applet icon — there is no "full screen" view for when you have a lot of networks in range.
• Its logic for remembering and prioritizing networks is just plain wrong, and the UI for editing this stuff is broken.
• It does a horrible job of guessing the authentication type of a network, and takes way too long authenticating.
• There is no command-line way to switch networks, and NM so messes with your Linux network connections that using typical command-line tools becomes painful.  I run Linux for a reason, you know
• NM is written in GObject/C.  I know GObject/C, but I also know enough to know that it's too much of a pain to go in there to fix any of these problems.

Enter wicd.  It seems to fix all these problems.  Like NM, wicd runs as a daemon and it is via that daemon that networks are connected.  It has a systray app like nm-applet that is written in GTK+ and easily integrates with GNOME, which is called wicd-client.  Unlike nm-applet, wicd-client provides a fast and ergonomic interface for browsing networks.  If you have a lot of networks in range, you get a nice window with all of them sorted by signal strength, and can easily set up "automatic connect" settings.