Rooting gives you superuser permissons, which will let your phone do things that it could not normally do. You would be able to install apps that require root. You would also be able to; browse the echos files with root explorer, you could freeze bloatware (apps pre-installed on phone when bought) with bloat freezer. Freezing the apps is great, you won't see the stuff you don't want in your app drawer, like all the sprint stuff. There alot of different things that can be done with various apps.
To get further benefits you would need a custom kernal and/or rom. Currently you should watch
http://heartheecho.m.webs.com/site/...ile?url=http://heartheecho.webs.com/index.htm I don't believe there are any custom roms yet for the echo, but they are under development.
I have my Xoom rooted with the Tachi kernal and Moray rom installed. I can install custom themes, I have the cpu/gpu overclocked to run at 1.4ghz instead of only 1ghz, there are tons of benefits to rooting. I can pair a ps3 dualshock controller via bluetooth, with blueputdroid, you would be able to do that on echo as well.
I totally reccomend it, they are details and instructions on that site I mentioned. There are a bunch of benefits and its pretty low risk. Most likely a complete wipe of the phone is needed and there is always chances of getting bricked. The chances are minimal but just know before you start that there are risks.
Xoom+Root = Perfect Match