Hi Alex, re: large file loading - thanks for sending the file. Over here I get:

MoI V4 beta Oct-17 : 15 seconds
MoI v3: 70 seconds
Rhino v5: 27 seconds to load + 43 seconds "Creating meshes..." delay on first view navigation.

Additionally over here the V4 behavior is better all around than both MoI v3 and Rhino v5. On Both MoI v3 and Rhino v5 the main window is just frozen during the load while in MoI v4 the window doesn't freeze and there is a progress bar and cancel button.

My machine is fairly old, Intel Core i5-2500K Quad core CPU, 16 GB RAM, with an old style spinning disk.

I'd guess that your machine is probably a laptop? My theory is that with MoI v4 making heavy use of all CPU cores your machine doesn't like that sudden spike in energy use and it throttles the processor speed way down.

You can probably avoid this by making sure it is plugged in rather than running on battery power and then go to "Power Options" in the Windows Control Panel and make sure that the "High performance" power use plan is the one that is active. It's probably currently set to a plan that sacrifices performance for less battery use.

Does that make any difference?

Also I will put in a setting for the next v4 beta so you can turn off the multi-core processing for file loading.

- Michael