Whoa, a case with a mod as one of the options. Me like...
Now all you need is a couple of cold cathode tubes to light up the inside with, and you'll have the sexiest case on the planet. Well, no you won't (you wouldn't believe some of the case mods I've seen - there's one guy who's fitted a PC, Xbox, gamecube, NES and Atari into one heavily modded PC case), but at least it'll be better than your average ****ty plastic box.
Like Cyrax says, all-plastic cases have a tendency to fall to bits, and yes they are impossible to put back together properly (they're not designed to be taken apart in the first place really). Metal/plastic combos are OK, as long as most of the case is metal. Plastic coated metal is alright, but it won't cool as well and it'll mean you can't earth yourself on the case as easily.
If you're thinking of buying a plastic or plastic coated case I would straongly urge you to look for an anodised aluminium one rather than painted/coated. They're just too god damn sexy...