I'm with JeffS - I do everything w/the data card b/c then I can see everything pertaining to one transaction in one place w/o having to scroll around. I cut and paste the address from here to my online postage meter, I make notes and actually read them, etc. I really really really find scrolling around in the spreadsheet a real pain. And BTW, the continued presence of the data card from 2.xx to 3.xx is most of the reason why I am so happy with 3.xx. So while I hear you saying you have no desire to do away with it, I want to reinforce my continued dependence on this particular feature so that you don't begin thinking you should get rid of it (based on comments like paintpower's)!
Mind you there are lots of portions of the data card and spreadsheet that I don't use that I know others do, but they don't seem to be in the way.
If/when you do update the data card, please do please do please do keep the ability to enter in addresses in one place (or even just a note area would do). If you break up the address into pieces I won't be able to cut and paste it but will actually have to type things in - a real pain.
--Melanie