Haven't been to Nanjing, but did go to Suzhou a few weeks ago and would concur with others here that it's a great place to go for a few days if in Shanghai. About 20-30 minutes by high speed train with plenty of services all day.
Re: transport from the airport to train station, I personally think that the maglev is a bit of a gimmick really. It is quicker but probably won't save you all that much time once the transfer at Longyang Rd station is considered. It's worth doing once as an experience, but after I did try it once I haven't bothered with it since. If I remember correctly, the Maglev station at Longyang Rd is above ground on a viaduct. You exit the station, go downstairs to ground level, brave any taxi touts milling around and find the subway line 2 entrance and enter the system again (i.e. ticket and security check). Not difficult, but not quite seamless either.