Curiosity, definitely. I'm interested in what is most popular but it would also be nice to see this change over time. You can tell something from the traffic in the bug reports area for each pack but you can also be lead astray - one pack may simply have less bugs, not less user activity.
I'm not looking to switch off of Unleashed. I'm just wondering if there are others I should be looking at for single-player play when I'm offline and not on my Unleashed server.