It does hold onto a bit of dirt, especially in the engine and under airbox areas, but to be honest, it's more than worth it. If it's good enough for the USAF to keep jets rot free, then it's good enough for me. I have a 14 month old K5, 8500 miles, including all last winter. No rot or corrosion apart form arond the fuel filler which is being replaced by Suzuki under warrenty next week
I do a strip down clean, then warm the bike up, and dose the bugger to death with the ACF50 stuff. Then all you have to do is a wipe down with a cloth saturated in it every couple of weeks.