Microsoft made some good improvements to the disk defragmenter in Vista. First they have setup a schedule by default for the disk defragmentation to run. This weekly defragmentation is a huge step in keeping our disks nice and tidy.
Because it is now automated by defaulted, they also gutted the interface making it very simple. Gone are the color graphs and if you really want those graphs I suggest finding a third party tool which might have them. They also removed the option to get the fragmentation analysis report.
Not trusting Microsoft to properly implement something, I went looking for the analysis report to see how effective they have been defraging my drives (particulary since I am using a laptop which I usually power off).
What I found was that the command line tool defrag was still around and can provide the analysis report. In order to get it run the following command from a command prompt:
defrag c: -a -v
This will spit out a simillar analysis report. The only difference seems to be it doesn't list the most fragmented files.
From what I can tell Microsoft got this feature right. Without me doing anything my disk is has a 1% file fragmentation which considering my disks back on XP would sit around 9% after defraging the drive is a preety good thing.