Right, I just used the 640i. Great sprayer. Plenty of grunt and no noticeable issues with it. The paint I used was as thick as porridge (you could shape it in your hands!!!) and it sprayed this with no problem at all. It has a max tip size of .23 but I used a .17 and it pushed this stuff through with no problem. The only thing annoying me is the bucket hook does not hold my 10 liter paint bucket under it
The controls are easy enough to use and the pistol that comes with it is plenty good enough. I used an extension and it is a handy piece of kit.
My only piece of advice would be to buy the high rider stand as it is by far the most practical. Also, with the high rider you get a solid aluminium intake tube that is less likely to build up with paint and then flake this paint off to be sucked up by the machine.