Wimsey's inabilities aren't really visible in the realtime of the books -- well, the problem crops up once in a while, like the breakdown he has in Whose Body, and in a couple of the books they talk about his "hangman's hands". But Busman's Honeymoon made it pretty clear that directly after the war he couldn't do things like ask for the kind of breakfast he wanted.

And you're right -- one of their most important shared traits is charming piffle, which can be used to edge around real issues if done properly.

I'd pay good money to see David Tennant in a monocle. With a dye job and some dialect adjustment he'd actually make an extremely good Wimsey, don't you think?