I went today to my local BB and used the iPad mini for about a half hour. Overall it seemed like a great device, felt awesome in my hands. I literally loved just about everything about it.
The screen is acceptable, definitely no headaches and it appears perfectly useable. Here's the thing though, and this is just my own opinion, Apple has spoilt me with the retina displays on my iPhone and iPad 3. I've really come to appreciate how graphics, and text especially, are rendered on a retina display. I noticed the degraded resolution on the mini right away. And I just couldn't get past that detraction. It reminded me of when I got the iPhone 4 and every time after that when I looked at a 3GS, the degraded resolution was front and centre.
Is this deal breaker for everyone, absolutely not. But I think, at least for me personally, had I never owned the iPhone or the iPad 3, I probably wouldn't think twice about getting the mini but as it stands, I'll wait till the next version where they'll probably put in a retina display. Just my two cents.