I remember a release when tracker was one of the innovations of Ubuntu. What happened to it?
Metatracker, usually referred to as Tracker, was introduced in 8.04 (an LTS release), but removed, I believe, in 9.04. I can only speculate as to why it was removed, but my guess would be multiple bugs, such as 100% CPU when the tracker daemon failed, or the slow start up on less powerful systems due to the indices updating.
I run it on my system and haven't noticed any slow downs, but my laptop is reasonably powerful.
There is a cool comparison of Desktop Search tools on Wikinfo.