I'd imagine the ride would be appalling on 18" rims - it ain't exactly smooth on 16's!
My 2005 6L Sport is on 215/35 18s and lowered 45mm. Ride isnt really that bad at all but there is a noticable increase in roadnoise. No rubbing issues either using a 35mm offset. Sometimes touches front bumper mount on drivers side on full lock if the car is fully loaded but ok apart from that.
Acceleration is slightly (and I mean slightly) dulled but its at lower revs on the motorway so it makes up for it there. Handling isnt too bad, the tyres are stretched so you do notice this is you are cornering very hard but in general not too bad.
There is only a 9mm difference in rolling radius between these and the 215/40 17 that many people on this forum recommend so its really not that big an issue. The speedo doesnt even read out. (I have checked this against a GPS Road Angel)
A lot of people rubbish things that they havent tried themselves so take advice with a pinch of salt, even mine as I dont know about the brake clearance issues!! Just check the offsets. 35-37mm on a 7, 7.5 or 8x18 should be fine.