I tried this initially, and it worked like a dream.. However, I
suspect that for someone who wishes to eventually give up windows
altogether, it might not be for them.. I couldn't see a way of
removing windows without removing the wubi install too.. Once I
realised I'd be sticking with Ubuntu, I opted for a totally clean
re-install.. Luckily I'd not been using it that long before I realised
what I wanted to do.. I suspect if you've used Wubi for 6 months or
more, and have your programs set up as you wish, it could be harder
then to get rid of windows totally..

I personally think it's a halfway house between a live cd and a full
install.. It gives the undecided people a chance to play with Ubuntu
for a while...