I asked myself the same question before buying a new one, but I grew up using air tools, so feel strangely at home [strikeout](and manly)[/strikeout] when working with them, but as you say they are not much use when working on bikes unless you're painting! They are useful to have about, but only if they hold the air and you don't have to wait for them to fill up, in which case they are a nuisance! I've used mine for blowing dust/water away when cleaning my bikes (not that i clean mine often!), inflating tyres, and i use the impact wrench when swapping wheels on my car from Winter to Summer tyres as its more fun and quicker than using the tyre wrench. I also used the impact wrench when i changed the brake pads on my Audi as there wasnt a lot of room to get a big breaker bar onto the caliper, and the bolts were bloody tight! but of course, for the cost of a compressor and impact wrench, you could just buy an electric impact wrench and a small compressor for your tyres