I dug the first issue of Cluster. It was action packed and moved quickly. Issue two slows down but only marginally. Honestly, they couldn't keep that pace up for the whole run. My favorite thing in this book is the action, the utterly ridiculously crazy and fun action. As the rest of the Bastards here pointed out there are a number of elements being pulled from here. While it doesn't give you something completely fresh and original, if you like those elements then you'll like this story (and I like those elements).
Every panel is filled with colorful characters and even more colorful backdrops. We get to see more aliens and a change of scenery as our protagonists trek back to camp.
The writing is still good, the plot is easily followed. The characters all sound like individuals (especially Slarreg, she's awesome). The issue begins in the prison then rejoins the main characters. The story weaves in a new character that is tracking down the main characters. This felt good and natural.
The end of the issue is two flash backs to the first issue, this just felt jarring after the rest of the issue being on the prison planet. If this is the first issue someone picks up they'll be able to follow the gist of the on planet stuff. But the flashback at the end would confuse them or maybe entice is the right word?