I don't use SugarCRM, but I might. For fun I have an instance setup on my super cheap bluehost account. Revisiting the whole thing now because Salesforce.com is just so DANG expensive. After not logging in for quite some time there was an upgrade notice at the top of SugarCRM. I wondered how to upgrade for a time until I saw that it was easy and there was a wizard. Click on "Admin" in the upper right and on the admin page there is an" Upgrade Wizard" link. It worked perfect for me as I followed the links, although on the very last click I got a memory error, it seems to have installed just fine.
SugarCRM still has the upgrade notice even after I upgraded, but the version it lists, 6.1.2, is older than the version I upgraded to, 6.2.0. And using the "Sugar Updates" link, also in admin, It does report that there are no more updates available.
As for moving from salesforce.com to SugarCRM. We will be giving up some funcationality, but not that much and the savings? Down from $2300 per month to $5 per month (We have 23 users). Wow! That's a lot of dough. Salesforce is awesome though, but like many companies we don't use the extra features that drive their prices up so high.
I gotta say that SugarCRM is no angel company either though. They have a paid version that isn't much cheaper than salesforce.com and the line between commercial and open source at SugarCRM is very blurry and there is a lot of talk about their eithics. They benefit greatly from the open source project but are sometimes stingy with what they will contribute back from the extras they add to their "paid version".