Not sure if this has been mentioned before, but since I couldn't find any such ticket...
Unlocking a database can be very slow (~15 seconds) when the computer is under load and the database key is secured with many iterations.
The problem is that when I enter a password and go on to do other stuff, KeePass jumps at me after several seconds showing me the freshly unlocked database. I don't mind getting the password dialog this way (when I mistype the password), because I intend to re-enter the password, but focusing the main window just disturbs whatever I'm doing for no reason.
This is less apparent when I want to unlock several databases in one go, but it's unpleasant when I just want to unlock a database and minimize KeePass (then I use the database through Auto-Type or a plugin).