Arabian Red,
I have both, a Throttlemeister and a Rostra.
Here's what you'll probably figure out soon about the differences...
I started with a TM. +1 w/ everything Joe said.
However, as w/ all throttle locks, the bike speed slows up hills, speeds up going down.
If you ride alongside someone who has a Rostra, it works just like a cruise control on a car, and will keep it very close to the speed you set it at.
So, if you're using a TM, you're constantly having to make throttle adjustments and watch your speed.
After a while, it wears you out, if you go far enough.
The Rostra will cost you around $300. But, you will find it to be the best farkle you'll ever put on your Connie. I've put several on for other guys, and they all love them and continually thank me.
I couldn't do without mine, since I ride long distances. But even a 30 mile commute at highway speed is still very nice with a Rostra.
Bob