I use AstonShell (and Menu) and yes it is a shell replacement, there are some hideous skins available for it but also some great ones. They also do a desktop manager called AltDesk which I haven't tried but if it's as good as their other products it will be superb.
http://www.astonshell.com/altdesk/The reason I haven't tried AltDesk is that I already use DeskSpace by Otaku Software. It may be a memory hog and it may not have some of the features of others but I love it - it has never caused me any problems and the visual appearance to me is the killer.
http://www.otakusoftware.com/I also use their task switching tool, TopDesk, which again I love for it's visual appearance.