I like Marcus Banks, and at age 26, I still think that he could resurrect a career if he could grow a brain, because he has the speed, strength and athleticism combination that few point guards can even boast of. He has a defensive rep already too. The best situation for him to excel is as an off guard offensively, and as a point guard defensively though...and I'm not sure most teams like to do the switcheroo unless they have a tall point guard. He can't pass, and he's turnover prone; so that assist per turnover ratio has gone to hell the moment he steps on the court, and really shows his very immature game. Until he grows a brain (doubtful), consider him peaked already, but I would think that if he had a more reasonable contract (again, the reason why contracts lower the value of players) he could be more valued--there are few defensive point guards with his combination of physical tools, and even if he's peaked to what he is now, he can still be useful as a spot player for matchup purposes. Not sure how Toronto will use him, but he's better than Willie Solomon.
That being said, Miami gets the better of this deal. Shawn Marion is just losing it, and he's just an expiring contract. I'm equally skeptical about Jermaine, but he's resurrected himself as a very good role player of sorts while in Toronto, and his combination of solid offense and ability to block shots is a highly valued around the league. However, if he does get injured and can't stay out of it (possible given his injury history), Miami may be stuck in a rut again. It's a risky proposition here for them. But talentwise, Jermaine is better than Shawn at this stage, and Moon is a poor man's Shawn Marion and will earn a role as an energizer bunny. As I said, I like Banks, but that's just one person's opinion, and coaches tend to disagree with me--although I understand their rationale behind it.