As far as beta releases go its just in the usage that tells you if its "safe" or not.
Some are absolutely fine, others can be a wee bit flaky, I have never had any total failures with them and i have been using them for over 2 years.
i have never had original versions on my bold 9000, 9700 or my works 8520
Any dodgy installer (ie: a bloated one with nasty intentions) will be picked-up here pretty quick but as far as reliability and features go - as already said, you'll have to gauge from the comments on the "leak thread" before deciding if it's worth the upgrade.