Haye's always been a talker, and never a very good boxer. Audley is massively under rated because people got into the hype and his career was ruined with promoters who just wanted to milk his gold medal rather than get him up to standard quickly against good opposition. He's had injuries, car crashes and wasn't young to start with, people also seem to forget Audley is bloody massive.
He's technically a VERY good fighter, I think there aren't many heavyweights who throw the combinations he does, but I think a mix of age, constantly interupted professional career and stupid promoters sending him out against bums for 3-4 rounds he doesn't have the stamina to throw as he can for a whole fight.
The sprott fight was impressive, took out one arm early in the fight, stood up to everything easily and the quality of the punch to finish it was pretty immense. I remember several of the early fights when he turned pro, after a few very quick fights IIRC he basically put his arms down and took hits (or tried to) against someone else for 5-6 rounds before he threw a couple combo's and his opponent was out. If he'd been up against better people quicker, and got up to speed before he got quite so old I think his career could have turned out very differently.
Thing is he's still huge, he's heavy, he can take a punch, when he wants to he can defend and he can throw a great combo.
Neither of them have really had a decent fight against anyone noteworthy IMHO, both have been treated like many british fighters by their promoters, talk a good game, never take the big fight.
Haye would get VERY easily beaten by either Klitschko, I'll laugh a lot if Audley puts in a good fight and wins, he's old though, but recent picks at press conference he looks huge next to Haye, he's only 3 inches taller but the difference looked far bigger, and Audley has a 8 inch reach advantage and unlike Valuev, might actually throw a punch in this fight.