[Tekker]

IMO, it depends really on what you're doing.

If you are learning a new song, but using chords and techniques you are already very comfortable with then I see no problem in going at full speed right off the bat, once you learn the song.

I think that going slow is more for perfecting techniques and this is especially useful if you are learning a brand new technique. For example, say you're trying to learn sweep picking, then you would want to start off slow until you get it sounding "perfect" at a very slow speed. Then gradually speed it up and making sure that you keep the same technique as you speed up. If you try starting off to fast right away, then it can sound sloppy because you haven't got the technique nailed yet.

The same applies to chords, strumming or anything. If you start off playing at full speed and it doesn't sound right, then slow back down and gradually speed back up. Doing the technique correctly multiple times at slow speeds will reinforce the good techniques.

Remember, that practice makes permanent. If you are practicing fast and sloppy, then most likely you will always play fast and sloppy unless you slow down to a speed where you can see what you're doing wrong and correct the technique.

-tkr