Rule of thumb is: if you have to ask, then you don't need root.
That's certainly a condescending rule of thumb, but it does have a certain sense.
Root allows you to change the system files and it allows apps to change system files (some apps avail themselves of root to do powerful things--remap keyboards, etc).
Rooting the Gem is having to use the Gemini Partition tool and that's a buggy device with ambiguous instructions--I did it last week, but I found the procedure difficult and nervous-making.
Once rooted, yes, you can make your changes in the system, but so can rogue apps, and the rubs with that 1) you don't always know something has gone rogue 2) the changes to your system can be permanent, even if you hard reset the phone.
So if you or an app screwed up something in the system, that's it--the only solution is to reflash the phone.
You have to ask yourself: is there something I can't do because my Gem isn't rooted? If the answer is no, the Gem does everything I want, then save yourself the hassle.
Jake