Many thanks for help / tips etc, especially to gleff - i will peruse the washingtonian guide as advised.

Weez - We're not there until end December, so maybe you could post your comments on the Swissotel when you get back for me

(and it's my first ever time trying Priceline, but it certainly won't be my last - when you're doing the tourist bit, it doesn't really matter which hotel you stay in, and the savings are sure worthwhile
)