Right now, only Louisville and Lexington, KY's two largest cities, have any open data as far as I know. Please leave a comment if you know of another city or have heard another one might be opening their data soon.
I prefer the bulk CSV data format, because if you want to you can import this into a GIS system, but it's harder to break GIS data in a CSV format for generic database loading. Having said that, some data is best output in GIS formats, like polygon area outlines (instead of point data).
I'd also like to point out what open data is. It's not just that it's data on a website in an interactive form, or a PDF to download. And it doesn't count if it costs money for a complete download. See the 8 principles of open data for a list, and I'd like to add that historic data is a ninth principle.
Louisville v. Lexington
So let's compare the two in the hopes of fostering some friendly competition and pushing each other to open more data.