I'm having the same problem..do you know if retina makes a BIG difference? I'm using the iPad 3 retina right now but I've never owned an apple product without it..
I've been with the iPhone since the 3G, and the original iPad. I've owned the 3G, the 4, and the 4S (currently), as well as the original iPad and the iPad 2 (currently). Just have to say that every time I see the Retina screen on any Apple product, I'm constantly amazed about the difference it makes. Since the mini is going to have about 167(if I got my spec right?) ppi, it seems like it'll be just like the mini itself - a tweener. Clearer than the iPad/iPad 2, but not quite Retina-worthy. I'm sure it'll make a big difference though, and since Apple's only improved on their image processing quality since non-Retina products, I'm sure they'll enhance the clarity as much as possible.
That being said, the iPad 2 vs. iPad 3 is definitely notable, even when not side-by-side. Make of that what you will with regards to the iPad mini. Hope that helps!