We have the Build 5442 (March 3) here.
Steam is/was always their testing ground, they had their alpha there I think.
25th was the next release and 26th again, today is the 27th -.-
And if you look at the patch notes:
1. They made it possible to remove street connections between towns.
2. A Sandbox mode where everything is for free and no economic simulation.
3. A mode where vehicles are not taken out of production.
If you use the timeless mod from train-fever.net, change 1/2 are included in it. More 3 than 2, but since you can run vehicles forever it is also an economic change.
Town and street names can now be changed or at least the pool of names it chooses from (available as mod).
Some Steam archivement fix.
US DLC updates.
Improved Russian translation.
The performance fixes are OK.
http://www.train-fever.com/forums/topic/release-notes/
p.s. OK, it is actual quite a lot, but give them a couple of days until the last fixes on the patch arivved at Steam, then they can build a proper new version here in GOG.
btw. Steam is known for the worst support of any software distribution platform :)