The MAIN advantage is that you can exercise the privileges of your US airmans certificate in an N reg aircraft. This means you can fly IFR (or ME/IFR) as the holder of an FAA IR. These are significantly cheaper and easier to maintain, so a viable option for a PPL. In fact all us 'ratings' are easier to maintain, you are not required to complete Multi checkride every year for example.
Its fairly easy to find US instructors in the UK willing to do a BFR / Instrument currency, and in fact there is a good organisation in Norwich which provide all services needed, including maintenance, training, FAA trust company, etc....Doctors are easy to come by, I got my FAA class 2 in Christchurch, it was free with my JAA class 2.
There are no doubt some disadvantages, however I think that maintenance costs will be about the same.
Rgds
EA
