Others here know much more than myself, my decision not to ride it is a personal one. It's common knowledge at this point that the support system is old, stressed, and should be replaced. It was a heated topic and has been since before the 2009 refurbishment.
Keep in mind, that this ride has been in operation almost daily since that refurbishment too, with just a few very short (just a few days at a time) closures. By the 50th Anniversary, it will have been over a decade of further stress to the support structure.
There has been quite a bit of discussion this too, take a read on this thread for more information (take note of Martin's post):
http://forums.wdwmagic.com/threads/space-mountain-discussion.910058/