We have a harken rollerfurling unit and the 163% genoa and have not taken that much of a speed hit. We still pretty much hit and exceed the polars without a problem. It is also much easier to use. If you are double handed or single handed racing the norm is to have roller furling for the obvious advantages.
In terms of Code 0 we got one for the express 37 I race on. It was a lot of $$, and the A-kites are better for a wider wind range and better angles. When you are in range to use a Code 0, however (which is a pretty narrow degree range for sailing) the boat takes off and you can completely wax all other competitors.
