Windows 7 is now better, I just tried to backup to a new external 2 TB drive. Comparing Windows 7 backup to Time machine is like comparing a Ferrari California to a Trabant. Firstly Windows backup is very very slow, backing up from an SSD to an external USB 3 device should be fast, very fast yet hours later the backup is still slowly chugging away, a quick Google and its clear lots of people are having issues. No only that but somehow it can work out Deltas (file changes) on files properly. Not much data on my computer actually changes however subsequent backups are massive filling a TB drive in only two backups given that the machine has got less than 1TB of data, I find that pretty odd.
So in Short Time Machine is full of win, where as Windows backup is a joke, I can only hope that Windows 8 boasts an improved tool.