I took out a Harley Sportster 1200 Forty Eight for a test ride and the engine was brilliant. Unfortunately the forward controls were a pain at low speed and grounded way too easily on corners (basically every corner). Oh, and you always felt like you were going to slide off the single seat. Apart from that it was great. Surprisingly good suspension and brakes alongside a nifty proximity alarm. I did write a full first ride review for another site, but I don't like linking to other motorcycle forums on here. Some people can get a little upset about it.
Having said that, instead of buying the Harley, I got a VFR800. Equally awesome engine, better brakes and cost far far less to buy