In the early days of NetworkManager I was not a fan. Fortunately it improved a lot and now it mostly does what I need (easier than anything else).
However there are a few things I don't like about NetworkManager and I hope the developers could look at these:
Tested on CentOS 5.2 with NetworkManager 0.7.0 from RHEL5.3. But same issues are reproducible with F10.
NetworkManager floods my syslog. And I hate it. Instead of only providing me with useful information it shows by default (it seems) a lot of debug information. I am all for debug information when there is something to debug, but showing debug information by default seems to give little faith by the developers in their own product. Does it really fail more than it works ? I doubt it. Please log only the minimum for users. Don't copy the dhclient info again, don't show me the individual internal phases, I don't care and my syslog is for more useful stuff anyway. And make it easy for people to enable when it fails to work...
Problems prefering one AP over another one. I have an access point that both has a WEP and a WPA2 ESSID, however at family I use the same ESSIDs for either WEP or WPA2 (depending on the case). Now I can't seem to make NetworkManager choose the WPA2 ESSID over the WEP one. What's up with that ? Why can I not choose the order of my preferred networks ?
Problems with non-unique ESSIDs. When I travel to family and resume my laptop that was previously connected to my home AP, it has difficulties reconnecting to the new AP with the same ESSID. I need to restart NetworkManager or kill and restart nm-applet, but it should just work, damnit !
NetworkManager does not support bluetooth modems. It used to in CentOS 5.2 using PPP connections (wvdial), but the functionality has been rewritten and we now have a nice "Edit connections...", however no longer supporting simple wvdial initscripts.
After resume 30sec delay before wireless starts to associate. Which means that in some cases applications fail in the meantime.
Maybe someone knows how to influence NetworkManager to act differently. Some of these problems have been reported on bugtracking systems.
Despite what seems like a rant, NetworkManager is better than anything I used before. But without some of the above problems fixed I am not sure it is ready for the technology impaired.