Hah, dont think of any of this as a waste of time, surely you are learning at least a little just by doing. And from what I've seen you've had plenty of people comment, if they havent been giving crits then they probably feel they have no need to.

Personally I don't seem to get many responses either, I don't take it to heart, some projects just attract more attention than others. Arran has stated it well, offer more crits on others work and people will be more likely to check your stuff out.

On your model, I have to agree with most of whats been said - the geometry looks clean, you just need some different shaders (bodywork & windows) and a little bit of 'dirtying-up'. Oh and I'm not sure how true to blueprints your exhaust ports are, but they look a little tight to the exhaust, and possibly a little too square. Wheels look cool!