I can speak from Kobo Touch experience that the developers really do listen to the Beta Tester feedback. While your own preference may not prevail, group feedback can and will cause them to tweak or sometimes totally re-jig something to make it work better for the broader user community. They can't always make the changes we'd like and I occasionally curse their final decisions (my way was right darn you
) but they do take the general feedback as seriously as they take bug reports (for example they changed out 2 or 3 of the 5 extra fonts they added to the Touch based on tested feedback). Not to mention you get to have and try out new features sometimes a quite a while before they are released to the wild.
Having said all that, don't go into it if you demand that your VOX works perfectly all the time and/or you aren't willing to reset to a previous firmware if something isn't working for you and you won't wait for the next beta release. There usually aren't a lot of showstopper bugs by the time they release it for testing, but they can occur for some people and minor "quirks" can occur that you may have to live with until they release the next beta build.