Avoid the metallics. Yellows and reds are very good from Vallejo and I would recommend them. Black (flat black not glossy black) is brilliant and one of my favourite paints. The best substitute for bleached bone is
GW's foundation paint Dheneb Stone as a basecoat, then bleached bone on top of that.
Vallejo has some very cool colours and mix pots that you wont find anywhere else. Wood grain wash is interesting, and the verdigris stuff is quite cool too. There are lots of things that let you change texture but I have not played with them yet (although a pot of 'crackle finish' is sitting on my painting desk ready to be played with). Vallejo also have a lot of hideously bright fluorescent colours which look fantastic but can only really be used effectively on small areas, some chaos models (bright daemons), or the Azonian 4th Hippie Guard regiment

I have all the fluorescent colours waiting for the day that I can actually use them, but it has been a while in coming so far.
Vallejo Game Color is best for miniatures but is thicker and needs more thinning. It has a slightly different finish and is more resilient to scratches than Vallejo Model Color (VMC). VMC has a wider range of colours and has the smoothest finish you will ever find anywhere. It also needs to be thinned before usage and the pigment and fluid will separate quite easily so you need to shake it like a madman before each use.