Project saved with ML is hanging v2.1.5 when loading it.

[micheus]

It won't open many of my files, and just hangs

Big files? How many polys?
With a object with ~230K polys it's a little slow in some operations, but I fell this in both 1.5.4 and 2.1.5 (no much difference).
And as I could notice, comparing your settings to one of those I used to test Wings3D (i5 650 3.5GHz - 4BG - Integrated graphic card) they have very similar performance (i5-650 vs AMD-Phenom-II-X4-940)

But, one thing that became reeeally slow was the Auto-rotate option.