Here are a few pics of my flats - they are Nukeproof Electrons. Light, grippy, strong and with a very nice low profile. They are in very good condition. I have only used them half a dozen times. The bearings are very smooth. Oddly I'm going in the opposite direction to you - having used spds since Shimano brought their first one out I thought I would try flats and find that I much prefer spds.
Review of them here
http://www.bikeradar.com/gear/category/ ... -11-45208/
As to Shimano shoe sizing my advice is to go a size up from what you normally wear. I'm normally a 44 but a 45 in Shimano. I have the flats version of the shoe you are selling. I'd swap those too if you were the same size...
Rich
