After my WordPress.com Stats plugin stopped working on cnyradio.com I decided to look for help. Many support forum threads indicated that installing Jetpack -- which includes a newer/better version of Stats -- would solve the problem.
Right after the initial install, things were great. But now, I'm having major problems. When I login to wp-admin, the dashboard widget shows "top posts" and the rest of the usual text that appears below the graph, but the graph itself never loads.
When I click on "Site Stats" to see the full-page version, it takes a lot longer than it used to. Sometimes I'll get "Stats can't be displayed at this time" and sometimes I'll get all the text, but no graph.
For a few days, my numbers also seemed to be a bit off-kilter, but comparing yesterday's numbers against Google Analytics, things seem to be okay now.
Other Jetpack comments briefly:
1) Would be nice if you could have Stats count people who are logged in "except" for certain users. (I don't want to count my own hits, but I require people to register in order to comment, and I want their hits counted.)
2) ShareDaddy would be more useful if you could have control over where the share buttons appear. Unless I'm missing something, they can only appear at the bottom of an article, and that's it. I'm using this on peterthedj.com but until they improve it, I'm still using an independent plugin (Wordbooker) to put FB "like" buttons at the top of my articles on cnyradio.com.
3) The other features seem neat, but so far, I don't have any use for them and I don't see myself going out of my way to begin using them.
WordPress usually does a phenomenal job with everything they do; I'm surprised at what a mess this stats problem has turned into, first with so many people's Stats no longer loading, and then Jetpack having its own problems.