Being a challenge to build doesn't make a kit bad. I did a GP Super Skybolt for a guy and it was a lot of work but came out beautifully. That sexy curved fuselage doesn't come easy! All the parts fit, the plans were good and the instruction manual complete. You really can't ask for more.

Many of the older kits seem to be fine at the beginning of a production run and then go bad as the dies dull. Laser cutting should end that problem eventually.

Ed is right about the kits from the old days, too. I have a set of Comet Sailplane ribs that were so bad (crunched from some real hard, dark, stringy balsa) that my grandfather just used them for patterns, cutting his own ribs from some decent wood.