I've had the Baroda firmware on my 350 for over a month and have never once had a glitch with using the reader. So I would say it is pretty stable. I use Calibre exclusively to manage my books on the 350.
The only hiccup I had with the Baroda firmware was trying to update it to the newest release. For some reason I kept getting an "access denied" error when running the install script on my Windows XP system. Nothing harmful happened; the install script just wouldn't run to completion. But I booted into safe mode and was then was able to run the script.
On the download page for the Baroda firmware, there is a link to the original firmware for all 3 current readers so you can always put that back if you want to.
The reason I took the plunge was because you can change the default font with this firmware. You don't need to adjust each individual epub and embed fonts in order to get the font you want. I now use either Georgia or Adobe Garamond Pro with my epubs on the 350.
As long as you follow the instructions to a "T" and don't try to do your own alterations to the baroda firmware itself, you should be safe.