I was also unhappy with UModel alignment until I discovered how to change the defaults. If you click the Styles tab and scroll to the bottom of the list, there is an option called Diagram Snap to Grid, and Diagram Grid size. I think the default grid size is 15, which I found way too large. I use 4 and get much better alignment now.

To avoid a very cluttered-looking display, I also turned off the Diagram Show Grid option.

There is a pull-down menu at the top of the Styles window -- make sure it says Project to apply your settings to your whole project, not just a single diagram.

Hope that helps!