I think the minis are great. As for the sliding scale, I believe they are aiming to make them look just about right compared to each other (Victory>frigate>corvette>fighters). Also, I'm sure they want to leave room for Falcon-sized ships between corvette and fighters and for Star Destroyers and possibly even SSDs on the other end.
For those complaining about quality, look at Star Trek Attack Wing. Also, the scale issue is far worse in that game...
I'm okay with sliding scale and if X-Wing is anything to go by, I think FFG will get it right.