I came from a manual Polo Blue GT to my current GTi PP, DSG and it's definitely a good move!
I liked the Polo and thought it a bit underrated. Sold it privately through Autotrader and it went quickly and for a good price, with a surprising amount of interest considering it was the summer holidays.
Only thing I would say is that I could easily get mid to high 40's mpg in the Polo, whereas the Golf averages low 30's on similar routes / speeds.
I really liked the Polo. It was a brain rather than heart purchase - the most amount of fun I could get for the money as it was a company car and costs heavily depandent on CO2. The mapping has changed since my last service (VW did say something about an ECU s/w upgrade) and there's not so much low end push, seems to need a few more revs recently. If I hadn't bought the Golf I'd be a bit unhappy.
Can anyone who made changes to their alloys after the build week was confirmed let me know if it slowed the whole order down much?