I'm sure it will longterm, but for now I haven't noticed huge changes in the SERPS. It is beginning to blend social media and regular links to come up with search results, such as live feeds of sites such as Twitter. The best way to hedge your bet for caffeine is establish a presence not only in the SE's today, but also the thousands of social media/networks available.
I can see some movements for my sites. Most of them went up but this might be due to my backlinks canpaign.
There has been a change (other than caffeine) about a month a go that MIGHT affect your long tail rankings. http://www.im-wizard.com/are-you-suddenly-having-problems-with-long-tail-searches/ It ultimately depends on the quality of your site. Caffeine, of course, could have a further effect on the results.
I really think the caffeine made Google more sticky for users. Which I'm betting they were hoping for. As a result, I have not seen any changes in rankings, but a hell of a lot less clickthroughs. Honestly clicks are down 20% on almost all my words without any change on my end or rank changes in Google SERPS. It's funny I gained 7 places on one word from 10 to #3 result and I actually see less clickthroughs even on that word.
I am seeing little fluctuations with my website keywords. Though the fluctuation is not much but almost every keywords have dropped by 3-4 spaces...
For my website one of the primary keywords ranking is improved after the Google Caffeine implemented.