We've done this to death on a recent thread. However, from the perspective of the aerobatic fraternity, I would again draw attention to Eddie Goggins' excellent article in the last Aerobatic News Review:
http://www.aerobatics.org.uk/Journal_Nov_07.pdf#page=39
Some of you may recall his survival of a collision at very low level during the Aero GP in Malta a couple of years ago; the article describes not only the event itself, but the events of a number of years which led Eddie to use the sort of safety equipment which saved his life, and also the kind of attitude required for it to be of use in extreme circumstances - if you're not prepared to use every last option, and fight for every last chance, then you're probably right that a parachute won't save your life, because you'll have mentally talked yourself out of using the option a long time before.
I find Planes49's comments particularly worrying. The implication being that he would wear a parachute 'when practising spins or stalls', but not when otherwise flying aerobatics because the only risk he sees is catastrophic failure. For me, and any other competent aerobatic pilot I know, this combination of sentiments sets alarm bells ringing. Either you should be happy recovering from any spin mode the aircraft has to offer as a matter of course during normal aerobatics, or you should be prepared for the consequences. You've also posting looking for formation partners on another thread - but seem strangely reluctant when the subject of formal formation training is raised. If you don't have enough regard for your own safety to wear a well maintained parachute, then I have serious doubts for your regard for the safety of anyone else six feet off your wingtip. So I'll pass on the formation invite, thanks. In fact, you'll forgive me if I'm a little blunt, but it might be the best bit of advice you ever get. The Yak 52 isn't a difficult aircraft to fly - and no more difficult to operate than an Arrow. But once you go off at the deep end, it has an extremely unforgiving side that can and will kill you in short order without suitable training. Some accidents have been tragically unavoidable, but the majority have been tragically avoidable, and from an entirely selfish point of view every time some - probably charming, likeable and thoroughly nice - incompetent stuffs one in, killing himself and often some poor innocent in the back seat, it pushes my insurance premium up. So please have a long hard look at where you're going with this aircraft.