Story - The storyline for Solty Rei is hardly original. An android girl appears out of nowhere to a group of protagonists, in this case the members of the Maverick Bounty Hunter Agency, and integrates into the group. Her past is slowly uncovered, revealing a (literally) galactic significance to her existence, linked to a dark secret in a seemingly innocent backdrop. Similar themes appear in Trigun, Trinity Blood, and Chobits, for example. However, I can't help but feel that GONZO have translated this into a feeling of security for viewers, not boredom. Given familiarity with similar storylines, there is more time to enjoy the character development, comic elements, and eventual dramatic conclusion.
Animation - Another masterpice from Range Murata akin to Last Exile. The female charcters have a natural charm, though the imbalance in the dark hues used for Roy Revant compared to other male characters was a little distracting.
Sound - Great mixing, very effective. Loved the opening theme, though the majority of English subs for this are a little lacking. Japanese lyrics don't always translate well.
Characters - The development of Roy Revant was superbly executed, but changes in the character of Solty were a little confusing. She had no memory to begin with, yet within a few episodes she was already cooking and laughing along with the crew. There were none of the existential questions of identity that one saw in, say, Chobits. (Granted this wasn't a large part of the plot.)
Overall - A fairly standard story, but very well animated and executed, another great piece of work from GONZO. Very easy to watch, would recommend to anyone looking for a nice one to watch.