Tracker sucks. Thanks, Tracker.
After using Gnome 3.6.2 for a few days I have noticed a significant slow down at startup. I love where the UI is going (especially if you actually select bluebird as a theme instead of adwaita), but at every startup or in the middle of the day (including when on batteries) my hard drive was grinding away and the CPU was used up by tracker-store. iotop informed that tracker-store was using up 99% of I/O for several minutes and top reported 99% of CPU usage at the same time. Not too big a deal if this is only happening once, but it has been happening every day on my Asus laptop on GNU/Linux. This makes me feel like I'm losing control over my computing (to a certain extent.)
Free software to me means – among other things – the opportunity to understand what my computer is doing at any given time and the power to not let someone else choose what it is doing at any given time. Non-free software makes me gradually lose touch with the tool I have a right to understand and master if so I choose. That's why I decided to stay away from non-free software as much as possible.
In many ways, this issue with tracker reminds me why I switched from MS Windows to GNU/Linux initially (and also stayed away from syncing magic like iTunes, besides the nonfree issue.) It's the feeling that your computer is doing something (especially lots of read/write) you have little information about and don't know whether you want it to or not.
Even after looking up what Tracker does on GNU/Linux, I'm not completely sure what it does exactly at the moment it's running: http://projects.gnome.org/tracker/
You can also find more practical information on tracker at the url below and how it is concretely used and the advantages for users, but this is still not what I'd expect from a PC for my work projects: https://wiki.ubuntu.com/Tracker
While the idea of indexing content and the practical examples offered in the Ubuntu link are interesting, it's only beneficial if you don't keep a tight control of your files. For instance, who needs to get their mp3s indexed automatically when they keep them in their Music directory and if they are using MOC.
Using grep and find for all of my search needs has been a great experience so far: endlessly indexing content when I'm trying to work is a real waste of time and productivity.
Frustratingly, disabling everything using /usr/bin/tracker-preferences didn't actually stop tracker from running amok at the next reboot. Killing the tracker-store process actually doesn't kill it for very long...
Finally, uninstalling tracker with apt-get (sudo apt-get remove tracker) actually removed a bunch of other packages (including tracker-extract, tracker-gui, tracker-miner-fs, tracker-utils.)
I was afraid of not being able to use Gnome Shell properly after that, but the next reboot was much faster, and my hard drive doesn't have to run its daily marathons anymore! I have not noticed any negative side effect.
In a sense, it's great that you don't need tracker to use Gnome 3 efficiently. That's yet another benefit of free software: You don't end up being locked with a single solution as is often the case with proprietary software. For this I am grateful to all the developers of free software I dislike and choose not to use.