I saw a BEBE ad at a bus stop and thought it was her, just looked it up and it was Mischa Barton. It doesn't look like Adrienne Shelly online, but it really looked like her at the bustop, and it made me sad.
I have only seen her film Sudden Manhattan, it was fun enough.
I will agree with you on Nathan Fillion. A great actor who unfortunately has been largely underutilized or been in projects that really should've reached larger audiences (ie. Firefly/Serenity).
I never watched Felicity, but Keri Russell was superb in Neil LaBute's play "Fat Pig" when it was done off-Broadway a couple years ago with Jeremy Piven. Maybe she should just do live theater (she looked incredible in person as well).
I also caught this a couple days ago and really enjoyed it. I will be shocked if this doesn't get a much wider release - it's really a good date movie and I can't imagine anyone not enjoying it to some degree. Keri Russell IS very good in this, and the melancholy tone is really effective.