I saw it in the theater, but I didn't know squat about it ahead of time. I don't think I knew what unicron was either. I remember, it was the summer between 5th and 6th grade. My mom took me and a buddy to see it. While I liked the movie, I remember being kinda bummed/stunned, partially because of all the deaths, but also because I didn't know anything about all the new characters. And I didn't have all the '86 toys yet.
I guess it worked as a marketing stunt, because I certainly wanted to buy a lot of the new guys. But half the fun of seeing a movie like that was going home and acting out the good parts with your toys, putting your own spin on it, etc. But if they toys aren't out, or you haven't had time to acquire any of them, it falls a bit flat.
I've seen the movie a ton of times, probably once a year for the last 15 years. My kids have seen it mutable times, even the wife has. So there won't be any shocking surprises, but the wave of nostalgia should be well worth the price of admission. The fam knows how much I'll enjoy it, so they're humoring me if nothing else. Plus it's a movie on a school night. What's not to love if you're 9 or 11?! Should be a good time.