There are very good alternatives, but this involves having to re-learn and teach yourself new ways to achieve the same things
That is a one-off. The best way is to go cold turkey on Windows.
Also, why dual boot rather than WINE (if it works for your apps) or running Windows in a VM?
One group of users for whom Linux is now very well suited are those with simple needs (e.g. people who just need a web browser, an email client, a word-processor and a media player). It easy to secure and auto updates.
Its a lot harder for people like those of using here to switch OSes because of the time we invest in learnings the tools we use - on the other hand, a lot of us will be using Linux or Unix server anyway.
One more thing. A lot of people seem to think that Linux means Ubuntu. There are a bunch of other desktop oriented distros including Mandriva (which I use), Mepis, PCLinuxOS and SuSE (Novell), some geekier ones that make good desktops if you learn them (I plan to eventually switch to Chakra/Arch), and a lot of fast and lightweight ones (for old hardware or speed freaks).
One things about the four points you list in favour of Linux, is that, apart from boot time, few people realise how much difference they makes until they have tried it. I am surprised you left out easy software installation, which is the biggest single advantage for me.