I'm not really sure about the printing, to be honest.
There is a fairly complete set of controls (for layout an processing), but I do very little printing these days. The last time I did any in Aperture I was mostly making contact sheets, and those came out a bit weird (probably because I was mixing aspect ratios). The few full sheets I did were ok, but it took a bit of fiddling. That, and my printer is/was a cheap all-in-one, so the results were OK, but nothing I'd sell.
Here is a screen shot of the Print dialog from Aperture. You can create more Custom settings to tweak things the way you want.
A photography blogger that I kind of follow has recently chosen to switch to Lightroom 4. You should probably at least take a look at it before deciding on a better photo editing app. It is certainly comparable.
His reasoning, however, is mostly a snit over the fact that Apple has not (significantly) updated the Mac Pro line recently (two years I think). He's jumping ship because Apple obviously doesn't care about professional users anymore (according to him).
Me, I say it's too early to tell. Apple has been focused on growing it's iOS market. Now that it is looking pretty good, there have been several indications that they are shifting their attention back to the computer line. If they are going to update the Mac Pro they will likely go for the win, and that will take something more than bigger chips and hard drives.
Tim Cook replied to an email complaining about the lack of Mac Pro updates. While saying nothing specific (remember they are doubling down on secrecy
), he hinted that there is something coming, probably this winter or early next year.
According to what I'm reading you can upgrade from Snow Leopard to Mountain Lion, as long as you're hardware is compatible and you've got the most recent Snow Leopard updates.
FAQ: Apple reveals more about OS X Mountain Lion - Computerworld