I think that you will find that H1xx users who have employed Rockbox typically are happy that they have done so, even in these "pre-release" days (there has not yet been an "offical release" for the iRiver players). I don't recall hearing of a single "bricked-player" issue for the H-1xxs, or any other hardware damage issue. (There have been a few reports concerning player shut-down issues when the battery has run down. I don't recall what player platforms this was with, and the solution, if there is an issue, is simple: don't let you player battery run down to near-empty.)
The most that I have faced in a year of using multi-user-patched bleeding-edge builds is an occasional player freeze, fixed by pressing the play or record button, or using a paperclip on the player's hard reset button. A paperclip is a nice thing to have around--I keep one in my case, just in case.
Actually, there has been another issue: untold time spent in getting improved versions of the software and in personalizing the player to my (as versus iRiver's) pleasure, including designing While Playing Screens and adding patches (learning how to compile code in the process).
More info. (loads, actually) can be found at Misticriver.net, in the Rockbox forums.
Enjoy!