Nope, the plugins I mentioned work fine on the free version, although I did extensively use the "solid" tools that are native only to the new "pro" version (Sketchup Pro 8 )-- just boolean functions basically, but it certainly is past due for them to be in Sketchup.
Sketchup can be a capable hard surface modeler -- it has it's quirks but for modeling non-organics it can be good (with some plugins of course)... I wouldn't recommend it if you need to do any decent animation or complex UV mapping though.
I think Sketchup gets a bad rep because it attracts newbies (since it's free) -- and generally they don't do such good work
There are definately a few hard-core modelers doing very solid work in Sketchup, you just have to look for them
I will say that Maxwell Studio is a must for me because, while Sketchup can model very nicely, it does not handle complex scenes and heavy geometry very gracefully... so I use Studio to composite my Sketchup models with sculpts from Z-Brush into scenes.
Best,
Jason.