I was pretty scared that the movie, which despite loving it and watching it over and over as a kid (I hadn't seen it in probably 15 years or more), would be cheesy and unimpressive (remember The Neverending Story? Terrible!) My fears were quelled early and extensively.
The live-action big screen adaptation of the Turtles' story really got it all right. The action was entertaining rather than watered down, the plot was compelling rather than contrived, and the late 80s expressions and music were quaint without being (too) cliche.
If you haven't seen it in a very long time or at all, it's definitely worth your hour and a half.