I have been dual booting for 3 years on every laptop I have had. I do and have done a lot of desktop support for XP / Novell / GroupWise, so I still keep a copy live and kicking for reference work and lab testing (SP2 for instance).
I always keep a DOS partition between the two systems for keeping my music on. For personal use I only use Linux.
I started with Corel Linux many moons ago, but always failed to get my modem working. I then went to Mandrake, then SuSE for a few versions, but was getting bored and more and more frustrated with what felt like the large and clunky KDE and was on 9.1 when my friend told me about Unbuntu, I have been happily here for a couple of months now and loving it.
I feel the Unbutu desktop is as good a windows for web browsing and for basic office documents and with utilities such as Firestarter and F-Prot, firewall and anti-virus have the same prescene and give peace of mind that such programs as Sygate and Ad-Aware or InnoculateIT / Norton etc.
I know for sure that the office where I work could go over to a Linux desktop environment, but unfortunately is a M$ shop and will be as they are retiring the Netware servers and going over to Windo$e!
Maybe one day I will have a completely Windows free laptop, with each day I suppose that gets a little closer.