Maybe it's just me, but I'm not sure how much better Apple could have made Maps before launching it. The thing that gets me is that I can only view driving directions fully zoomed out or fully in (rather than being able to zoom in and out). However, in terms of map accuracy, their data is coming from TomTom/Tele Atlas. Google's data is better. Not only that, but Google has been working hard on local search. Apple simply doesn't have that data. I've really yet to hear how Apple could have launched a better product. Google has been getting data for many years now and when Google Maps launched, it didn't have nearly as complete data. As users used it, data improved. Apple has less chance for improvement because Apple doesn't do local search and non-phone maps in the way that Google does.
It's why I think Apple should make a web interface to provide an easy way for people to add businesses and make corrections via their browser.
I mean, I vaguely remember when Google Maps switched from Navteq to Tele Atlas for a while and users disliked the Tele Atlas data. However, if you don't own your own mapping data, you need to buy it from someone selling. Given Nokia's ownership of Navteq, it seems unlikely that Apple would have gotten that data.
Other than improving the data over time, what else was egregiously wrong? On the data side, I think it takes time with the app being used by the public to correct that. If they were to make the hard decision not to ship Apple Maps, would the data be in pretty much the same situation a year later?