I have been using Ascent since I got my Edge 305 two weeks ago. I previously played with the demo (limited to 10 entries I think) that comes with a sample datafile filled with a few rides.
I was previously using a Polar 725 with a software from England called iSmartTrain that I liked a lot so I knew what I was looking for.
Ascent is the main reason I switched to the Edge at this time, I liked the idea of the GPS with the feature that allows you to measure a ride to a previous one on the same route. Yet the available software from Garmin didn't inspire me much. I found them clunky and missing the info and graph I was used to.
Ascent as it was had 95% of what I was looking for plus a very nice link from GPS data to maps (hybrid, satellite, topo, streets). Plus the interface is very well done both esthetically and functionally (I am a software developer myself so I can be picky). The icing on the cake was the way the author responded to suggestions I made on the forum even before I had my Edge. Rob is working very hard on this thing and posts updates almost once a week.
I have now registered and am totally satisfied with it. I highly recommend Ascent as it's way ahead of anything offered by Garmin at this point.