To add to what others are saying, always thin your paints! Painting straight out of the pot is going to get you clumpy, streaky, detail obscuring results.
Regarding the new GW paints: there were two batches that went out in two different bottle styles. The first batch did not seal well and will result in your paint drying out (planned obsolescence?)
Regarding craft paints: like Dave said, they have a low pigment count. They're a cheaper alternative, but you're really paying for a lot of medium and not a lot of pigment.
Yes, miniature paints are expensive, but the great thing is that you don't need every color under the sun - limit yourself to a color palette. Not only will you spend less money, you'll have a cohesive army as well. I made a big mistake back when Vallejo originally put out their miniature line - I purchased the entire line of paints. I'm pretty positive that there are paints in that set that I have never opened, let alone used...