I had a bit to do with Warranty Direct a little while ago. They seemed alright ont he surface but there were a few qualifiers in the smallprint which eventually put me off. I think they're a reputable company though - one of the national newspapers uses them to underwrite their own 'special offer' car warranty. I think it's just a matter of being reasonable in your expectations - knowing what you want and the bare minimum you'll settle for, and also being very vigilant of the t&c's and particularly the exemptions. If there is something you are specifically concerned about then email a query so you have a copy of a written response from the warranty provider.
Big firms often try and rely on the intimidating nature of their reputations in pushing around the little guy but often, in cases of litigation (if it ever came to that) a principle of reasonableness can apply - i.e. is it reasonable to expect the consumer to find the clause in this place if it's well hidden, is it a reasonable clause, etc? Although you might not prevail on the legal technicality you can sometimes find some middle ground on this basis. The problem is that if a legal technicality stands in your way it takes a protracted amount of time to get to that point (and expense!) This is best avoided by knowing where you stand in the first place and being sure you have the cover within the t&c's that you want/need.
In the end, I didn't go for the extended warranty cover as I felt I just didn't need it but I think if you know what you're getting in to then it's not all bad. Of course there are dodgy charlatans out there but 'trust' isn't often applied to the insurance racket! What other industry can say - 'you give me loads and loads of your money when you're alive... and when you're dead, I'll give it back!' Brilliant!