I just installed PIWIK
 

Anybody else using it? I am still using GA on some of my sites, but owning my own stats data instead of google just seems proper

not used yet

I might have to give this a try.

How is the ease of use? And how does it compare?

it was easy to install and its easy to dig through the stats. Doesn't have all the features GA has but it seems like they are updating it on a regular basis.

I was reading on the forum that there might be issues with very high traffic sites seems they probably need to rework some tables in mysql.
http://forum.piwik.org/index.php?showtopic=1435

One thing I would like to know is. Can you view total unique visits for all the domains that have been added to it? I plan on adding several hundred small websites and would like to view the totals daily to see how the whole network is doing for traffic.

I use Mint and GA together.

I saw that thread also, he set it up on a subsite of archive.org, and used this "I set up piwik 0.4.3 on its own Athlon64 dual core 3800+ machine with 1GB of memory"

Im no server pro or load expert but isn't a gig of ram quite low to run a analytics script that is running on such a large site?

I guess you are talking about this?
http://haveamint.com/

how much does it cost?

$30/site

I have been running Piwik on a variety of sites for almost a year... it seems to work pretty good. The newest versions are way better than the old versions were... that's for sure.