Layout- When analysing a piece of design if the the layout has no uniformity and is hard to follow or read (unfunctional) is a bad thing. But if it's clean, minimal and easy to understand it's good.
Function- Again if it serves a purpose and isn't a complete mash up of randomness that had no form and is absolutely useless and lacks purpose or direction it's a positive.
Colour- Garish, overuse of colour is a real put off, but if it's minimal and desaturated it's fine. I only use a bright garish colour if it's kept to a minimum and used as a contrast to the main copy.
Concept- If it's a fun, unique concept this is always a bonus, but if it's really boring just like a bog standard book that has no exciting pop out or designs or colour it's a waste of time.
Design skills (Quality)- Obviously if it's a print on some lovely high GSM stock which is well printed it's always going to look better, but design skill wise you want to see something that looks simple but obvioulsy has a lot of thought and effort put into it to make it look so simple. But when it is just simple and there's not thought and you can clearly see the design process and skill is lacking through be it lack of technology knowledge or printing, it's bad.