(Download at bottom of post)
Listing all the changes/fixes/additions here would be silly, and they can be read in the release notes, but I think this works as a quick summary:
Release Notes wrote:
This second beta expands on the first in many respects, notably in graphics. All building (temporary damage frames), vehicle and infantry graphics are in now. There are also a few game mode additions: Retro mode changes the voxels to mostly remapable versions, Contraction mode removes all the Counterstrike/Aftermath Expansion additions and Retro Contraction is a combination of the two.
Units I missed the first time round like the Chrono Tank, Flamethrower and Missile Sub are in, the Shock Trooper now has the correct sounds (how I missed those I don't know), alot of weapons screwups are fixed, etc.
I started doing new terrain, but have only done the "clear" tiles and one map. This doesn't break any of the RA2 standard maps so it's okay.
Some screenshots (mostly in "Retro" mode):

An early Allied base.

A bit more advanced.

The Allies stage an amphibious landing with Destroyer and Cruiser support.

Tanya's got her work cut out.

Some Rifle Infantry stage a last stand, and don't do very well at all...

A pair of Chrono Tanks on anti-Ore Truck duties.

A Soviet Base

Got Juice?
There are one or two issues I know of:
Soviet Sidebar graphics glitches.
War Factory exit problems.
Mines are visible, this will be fixed using RP in a future version.
Torpedoes don't work on the new terrain (though the new terrain map doesn't allow naval forces so you shouldn't see this).
New terrain is far from complete.
Map start location numbers barely visible.
The download page.
Revora is being a bit slow at the moment so you might have to bear with it.
Non Revora mirror thanks to Raminator.