Just wanted to say thank you to everyone for their input.
We ended up getting a nice suite at a Marriott on Dupont Circle with $$ rather than points - the IHG hotels just didn't have suites bookable via points, and booking two rooms with points ended up being more expensive than the Marriott suite, which we found at $259/night - perfectly respectable for three people and two rooms, I think (unfortunately we didn't have enough Marriott points for it) We opted to stay downtown to minimize hassle, since we're only in DC for 3-4 days and want to make the best use of our time - especially since most of the things we want to see are downtown, rather than virginia or the outskirts of time.
re
ublic transportation, I think you have a good point in that 'usable' for your morning commute is not the same as 'usable' for touristy travel. With one, you know how much time to allocate and bring a book, and with the other, you have a limited amount of time and want to spend it best. That's one of the reasons we went with downtown.
I think we'll be visiting the Smithsonian museums, national mall, folger library, and (hopefully!) white house. If anyone has any other suggestions for things to see that aren't obvious (i.e. aren't the #1 recommendation on the Wikitravel page), feel free to throw them at me, I'd be happy to take them into consideration.