Hello.
I tried Ultradefrag 5.0.2 yesterday for comparing purposes against Defraggler. It has a nice Quick Optimization feature that works quite well and fast. I'd love to see that in Defraggler (I think I already asked for this in the DF suggestions subforum).
On the other hand, Ultradefrag GUI is ugly as hell. Ultradefrag also put two files at the root folder of every partition. Annoying.
Anyway, it seems a mature product that does its work and it's free. Not bad.