I'll start by saying everyone who lives in Toronto should try it once. After that, I say you're on your own.
There's a lot of mixed feelings on The Old Spaghetti Factory reviews - so I'll try to be a bit specific.
1) The atmosphere is fun - not great, but fun. It's just a little too unkempt for me, but it's still designed in such a way that you can enjoy yourself if you don't take the venue too seriously.
2) The food is plain. It's not horrible (I wouldn't liken it to toilet water!) but for Italian I would say it's very Americanized. I look forward to a bit of pizazz on my plate (if not in presentation, at least in flavor). You don't get that here. I feel that they stay away from too many spices in order to appeal to a grander audience, but in doing so disappoint people looking for a real Italian meal.
3) I got really drunk during a dinner with my wife and family, and I had a lot of fun. In this regard, the OSF is great. The wait staff aren't up on high-end protocol, but they know how keep you happy and give you your space.
I gave it two stars because of the menu, but the atmosphere can easily bump it up to a three. Like I said: try it once, then decide for yourself.