Captaincy is one aspect of cricket I never think you can really judge on results. The only data-based way to look at captaincy is in terms of a team wins and losses, and given there are so, so, so many other factors that contribute to the result of the game, I think it's a waste of time trying to look at it statistically at all. The only inference you can make from any win:loss ratio is that if a win:loss ratio is excellent, the captain is not abysmal. No matter how good your team is, if your captain is abysmal you will still perform poorly.. I do think it's quite possible to perform well with a poor captain though, and I definitely think it's possible to perform poorly with a good captain.
Essentially that means you can only judge captaincy through watching captains go about their business and deciding whether you think they are making the most of their resources or not. Unfortunately though this opens up the opportunity for huge degrees of bias from anyone with an agenda or a nationalistic preference.
As far as Ponting as a Test captain goes I think he is a superb leader of men and an average cricketing tactician, which translates into a pretty par captain in the grand scheme of things, depending on what sort of captain the team needs of course. He's precisely the sort of captain you want if you have a lot of quality players with big egos in the team as he's a very uniting figure and the tactics are less important if you have world class players at your disposal who are all committed to the team cause (the latter of course due in no small part to Ponting). I don't think his captaincy is really a particularly big factor in rating him as I do believe a lot of players could do a similar job, but I don't think he's the prank-captain some here seem do. Trying to prove it either way with match results is futile though unless we know what Australia's win:loss ratio would have been under a different captain at the time. There's no way of quantifying how effectively he used his resources without watching him do it.