F/F these days is about as reliable as Wordpress in terms of version longevity!
Within the space of just a few months we have gone from v3.6.27, to my mind, probably the best and most stable version of F/F ever, to v10.0.2...
Change for change sake? Trying desperately to compete with Chrome or IE9?
I for one, don't believe that F/F 10 is any less likely to hacking than V3... if the bu**ers are going to get you, they will get you anyway...
I asked a similar question the other day on a specialist forum about the multitude of updates to F/F and the best advise I got was to be give it up in favour of Opera or IE9...
Just my two centimos worth....
pp