I made it to the end of the Estherian ruins before I got bored of the first. The second is far more interesting. I'm actually really excited to see where my build is going, especially seeing that I've just realised that I'll have enough skill points to get some cannon skills.
Cannons are amazing, by the way. Anyone that watched the Yogscast playing the beta should remember Simon's love of cannons. I didn't really understand it until today. I picked up a cannon that had a really high rate of fire and I was tearing through enemies by swapping between loadouts. My boss strategy currently consists of kiting the boss around and shooting it whenever I can until I build up enough charges to tear through their health with the default slam attack.
Engineers are fun.
e: But I'm definitely up for co-op sometime. This kind of game is much better with another person. Sadly I have no friends to play it with.
Sadly I have no friends 