I have a Q5 which got delivered yesterday in UK (from Lambda-tek.com), I don't have any other projector to compare it too though unfortunately so I'm pretty much comparing to my TV, but first Impressions are It's pretty amazing for how small it is!
It's great for watching TV, but you need the room fairly dark.
Negatives that I have noticed are that it's quite noisy - and in 'Bright' picture mode the fan is really noisy (note this is not Eco vs Normal mode) it also has a low power mode, no idea what this does though as seems to make no difference.
I'm only projecting onto my wall which is kind of eggshell white and slightly glossy at about 80 inch picture, and I noticed that the blacks are not very black (in all light conditions), and it struggles with dark scenes in general (Maybe an issue with all pico projectors?, contrast ratio too low?)
It also get's fairly hot, i have a metal USB stick which i used to plug in a film, and that was really hot to touch after 20 minutes.
Minor gripes, also it comes with a case for the projector but not case for the power pack.
I've not seen any rainbow effects or soft focus patches.
PC text also seems fairly readable.