Got my 20's installed along with the Eibach ProKit springs:
Wheels are CSA Emotion (which are basically a Vossen CV5-style wheel without the exorbitant cost) in 20x8.5 et35 (F) and 20x9.5 et45 (R). Tyres are Achilles Desert Hawk UHP in 245/45r20 (F) and 275/40r20 (R).
I went with a staggered setup mainly for looks, but I'm happy with the ride and handling as well. Ride quality is very close to standard, with excellent small-bump compliance thanks to the progressive rate springs, while larger bumps (such as speed humps) are handled with slightly more firmness but certainly not uncomfortably. There is marginally more road rumble than before, but that's probably down to my choice of tyres versus the stock Toyos, which are more comfort oriented.
The big difference is in the handling, which feels much flatter through turns and under brakes, while also providing noticeably more lateral grip. I was initially concerned that a staggered setup may result in excessive understeer, but that doesn't seem to be the case at all. I even tried to provoke understeer by pushing it hard through some tight turns, and the handling remained well balanced. Overall the car feels more planted on the road and encourages you to have a go through the turns, which is great fun.
Of course the main reason I bought the wheels was for looks, and I am quite pleased with the way it has turned out aesthetically. The wheel design is quite conservative, but the fat rear stance gives it an aggressive edge that helps it to stand out from the sea of skinny-wheeled CX-5s. I'll post some more pics when the weather improves (it was dark and overcast when these were taken).