Short Early Access review as of 25/13/2015.
4 months after my initial review, I am writing it all from scratch.
Spent a few hours playing Race to Mars today. I see many improvements. Managed to assemble an unmanned rover and a small liquid rocket. Did not make it in time to fulfill the contract that I got via funding grant though.
The UI still needs optimization, especially in regards of opening and closing windows/tabs. However, it is mostly fine, actually. I have reflected my recommendations here:http://steamcommunity.com/app/257930/discussions/0/618457398957456040/
Given a current state of the development, bugs were expected, and they are there. Not all the features are implemented yet, and I wasn't even able to launch my moon rover. Nevertheless, I kinda liked the process of researching and constructing it.
You get LOTS of options as to what to do in this game, and how you do it. The variety at this point have actually impressed me. You can either buy equipment/components, or research and build them yourself. There are contracts, grants, and loans. Unmanned programs, manned ones, satellites, landers, impactors, orbiters, rovers, it's all there, even though not entirely finished.
Rocket and payload construction/configuration seems promising. You select the equipment which changes the stats, including payload weight/mass to LEO/GEO/Moon/Mars. Some calculations seem to be bugged at the moment, though. But you get the idea that you can persue certain weight limits with payloads and make rockets for different purposes, finetuning their efficiency/cost via components and number of engines/control mechanisms for each stage (!) etc.
I like such variety.
As I wrote previously, the game itself feels pretty atmospheric, due to cool ambient music and good visuals. Have yet to see how rocket launching works though, and how missions in progress work.
Be warned though, this game is indeed early in development (thus Early Access), and I personally can't call it fully playable now. I did play for a few hours, but there's not as much to go with as it is intended by developers (though their intentions can be seen). A lot of things are under construction and not working.
I hope developers will finish this game, and it'll be in good shape. Keep it up!