Hi Marc,
Nah, the free version of sketchup can do everything, modeling wise, that the payware version can.
It's in the exporting and such, that the free version falls short, the compatibility with other programs and popular formats and such.
But as a modeling tool, it can do almost everything that the big expensive brothers can. But when it comes to the further development of a bare model into something that can be used by other applications such as games, that's where Sketchup falls short unless you use a combination of programs to fill in the gaps.
Fred.