I've learnt quite a bit, and will get round to blogging things sometime, but the main lesson is - most domains earn nothing from adverts while on sedo or other marketplaces, and a decent offer of $500+ should get you almost any domain you want.
If it's a domain that's worth much more than that (e.g. insure.com sold for $16 million), then it would have been bought long ago regardless of domain squatters. It would just have been used by some other business, so you didn't really lose out.