To check some effects of personalization, I have one browser where I have the Google Toolbar installed, haven't flushed cookies in quite a while, haven't disabled web history, etc etc... but with no log-in to a Google account.
Google has tried fairly aggressively to get me to let them access my local information, and while I've refused, it's very clear that they're use cookie data, IP data, and possibly even ISP connection data to pinpoint my default location fairly accurately.
I'd posted a while back that they had improved map box results quite a bit and postulated IP data. This was before they were using search history or had announced personalization as the default, but not before they were using cookies or IP data.
Local searches are where I feel that Google has thus far focused most of its visible personalization efforts.
Just before they announced that personalization was the default mode, Google also tried to get me to use their Searchwiki, which I haven't had time to test. I'm fairly sure that this is another area which may, over time, affect "non-personalized" results (if there is such a thing), or at least to provide correlative data. I haven't had time or inclination to even go near their Social Search.
For regular plain vanilla searches, non-geo based, I've been running some tests on this same browser setup, frequently repeating many non-geo searches for the same queries (that might logically be searched daily)... and then revising them via various patterns to bring different sites to the top... and I have had no indication whatsoever that these searches and revisions are thus far influencing the serps, either what's sent to me or what's sent to anyone else.