I lived in Baltimore for 4 years and watched a good number of Wizards games, and I'm going to assume a lot of people haven't actually watched Arenas play, but merely critique his low FG% and quirky attitude in the media.
1) Arenas is a helluva basketball talent. He has almost infinite range on his jumper and can hit it from any spot on the court. He also has a great first step and can change direction on the dribble fluidly, which imo is the big reason he gets to the line so much. He's a tough cover for any defender. He doesn't shy in crunch time. This guy enjoys the spotlight, and plays better when his games are nationally televised or his team is in the playoffs.
His shot selection though is definitely in question, and I feel this is partly because he feels like he can make any shot, and starts chucking up crap instead of looking for a better opportunity. Moreover, I feel Eddie Jordan really stunted his growth in DC, and his game never really matured.
2) He isn't a lockerroom cancer like Marbury. Arenas, at the least, gets along with his teammates, even if its at the expense of being the "class clown." Marbury was the anti-social nutjob that never seemed to befriend any of his teammates.
3) I haven't really watched him much since his return from knee surgeries, so I don't know if he's lost some of his explosiveness. His FG% has been worse this season, but it's never been too high to begin with. However, I've always felt that if Arenas had a true alpha dog to defer to, like LeBron, his FG% would improve, much like Jason Terry's did when going from Atlanta to Dallas.
If his contract gets voided, he's a risk worth taking on the cheap. I'm talking about anywhere from veteran's minimum to MLE. While his felony gun possession charge may impact your view of him, it might actually be the wakeup call Arenas needed to finally mature as a person and player.
If it doesn't get voided, Washington will be looking to trade this guy ASAP, and would probably include picks or young players to do so. If we could get Arenas for 1st round picks + JJ/Curry, it's definitely something Walsh would have to consider, especially since it preserves our cap space for another max AND Lee. To reject a trade simply on the grounds that you don't like Arenas as a person is a Dolan-like reaction. I would really only make the trade though if we got LeBron. I wouldn't want to build around Arenas, but I think he could be a great second fiddle to a superstar.