Painting-wise they are very nice models with loads of nice details all over. The standard martian paint scheme of red and silver really looks good on these models and the martian ironearth paint makes for an excellent base. My first squad of rangers are below to show how they look painted.
I also recently had a chance to play a small 750 point maelstrom game with them as well and these new units are good, I was only using the rules from the white dwarf as it was before the codex release so I wasn't able to use the doctrine imperatives. The rangers work really well as back field units with their extra range over most standard units and their ability to pick you special weapons and characters being very useful, while the vanguard proved their worth as a support unit for dragoons, allowing them to take down a chaos lord easier by lowering toughness. The additional rules available for the codex allows you to improve either BS or WS (sometimes to the detriment of the other) and if using the special formations and battle-forged force organisation chart gives them crusader and scout (without outflank).
This is just a little look at them, I'll do a more in-depth tactica and review when I've played more games with larger forces. I will also do posts on the other types of units when I have made them and had a chance to play a game with them.