What is the most important feature of kitchen cabinets? Do you prefer custom or stock? What color and what style is the best in you opinion?

The most important feature is space. Small, narrow, or shallow cabinets are almost useless. Stock cabinets are cheaper, custom are usually better quality unless you cheap out on them. It depends on your budget. Personally, I like cherry shaker style doors. The type with a bevel on the inside edge, not the square style.

I prefer stained wood. It's a classic look that can go with almost anything. I don't particularly like painted wood though.