Q: Even though my 2009 MacBook Pro meets the system requirements for upgrading to Mavericks, can anyone tell me if it's actually a good idea to do so?

Well,

If you invest in a fast FireWire 800 connected hard drive, you can test drive Mavericks by installing it and booting from an external hard  drive.

Another way to test drive Mavericks, WIth an external hard drive you could clone your current system and data to the external hard drive as a backup that is, also, still a bootable system using a data cloning app like

Carbon Copy Cloner OR SuperDuper.

Then just download and install Mavericks over your current system that is directly on your MBP.

If you do not like Mavericks, then it is a simple matter of booting to your clone OS X Snow Leopard external drive and cloning that back to your MacBook and you are back to where you were before the upgrade.

Other things to keep in mind.

Make sure your MBP has, at least, 4 GBs of RAM installed.

Make sure you have enough internal hard drive space.

Make sure you have NO antivirus apps installed on your MBP.

Make sure you have NO MacKeeper or any other types of hard drive "cleaning" or "tuning" apps.

Once you have installled Mavericks, make sure to update ALL installed software, Internet web browser add-ons and installed extensions.

Also, if you have any connected, third party periphetal devices, you will have to make sure to update all drivers for such devices.

I have a 2007, also with 4GB, and Mavericks seems as fast as, or perhaps faster than Snow Leopard. Others have said not, although perhaps they were running incompatible software.