A year ago I was one of the ones complaining about the speed of FTM 2012. While they have done nothing about the time that it takes FTM to load, they have made significant gains in the time it takes to generate and open charts and reports.
As for the time it takes to navigate around the various windows to review or manipulate data, the speed is quite acceptable.
If speed is your main concern in upgrading, I would say it is no longer a problem. BUT it is my understanding that FTM 2009 and FTM 2012 are not that different.
There is one reason for upgrading. If you have a very old computer that is on the verge of dying, it may be easier to update FTM now, and not have to get use to the horrible Windows 8 interface and the new items in FTM. Also FTM 2012, which is going to be updated through out 2013, will run on Windows 8, I don't know about widows 2009.