Sorry guys, I ended up falling asleep when I got home from work last night, but SebM pretty much summed it up. The metallics are horrid, but the rest of their colors (albeit a small selection) are already thinned enough that you aren't blobbing the model with paint. I also use a mix of both GW and P3 (mainly due to the fact that some colors are just easier bought than mixed from what you can muster up). P3 does indeed have a small selection compared to most out there, but I find their colors to be more vibrant than GW and Coat d'Arms (Not to mention cheaper). The P3 primers are also pretty nice (I switched to them after I had some horrible accidents with fresh GW primer cans).
I believe P3 does have a selection of inks/washes, but I have not tried them, as they are not available at my local game store. I have heard they aren't as good as GW's, however.
The P3 wet pallet is something I will never paint without. It gives enough moisture to the paints to keep them alive for several hours (if you ever need to take a break or go to someone's house, leave the shop, etc.) and also waters them down enough that you can blend VERY easily on a model.
Side note that I just remembered...P3 white is rather thin and does not cover very well (of course it might just be me, but it seems very...meh). I'm sure SebM would agree with me that the white is likely to have been made specifically for highlighting and VERY small areas...because that is about all it is good for.
Testors

...How can you stand that horrid paint?