macbook. Light portable and reliable.
One of the best features is the time machine backup system. I use a 250g 3" usb hard drive and everytime I plug my macbook into it at home it saves my entire drive completely automatically. Then you can travel back in time to your computer at a date in the past to recover stuff.
An if you really really need to run windows programs (like accessing our company server
) - you can install windows in a small partition and run windows in a window whilst using the mac osx! (you can also drag and drop items between the two).
And no viruses, it's stable etc etc....