Marlton was a genius character. Funny, intelligent quotes, and many subtle hints towards a past being bullied or working with other organizations. Very well voice acted to boot. Magnifique.
Misty is an utter failure character-wise. Transparently trying to create a female Dempsey with none of the charm. An annoying voice is punctuated by a ton of "I'm so cool" and "I'm a masculine woman look at me" stuff. Did I mention she was trying too hard to be Dempsey? Yeah, that comes up alot. In addition to not even being well written, with seemingly fewer lines than the other characters, none of which are any fun to listen to, and lack creativity.
Russman. He's actually quiet (I haven't heard many quotes from him despite playing as him alot), but he seems to be pretty cool. A murky Alzheimer-addled past gives alot of oppourtunity to flesh out the character. I hope they don't push an "I'm old and homeless, hur hur hur" thing on him because that would ruin the foundation they could build so much on.
Sam is... an odd one. I enjoy him as a characcter, with many funny lines. I like the "paranoid conspiracy theorist" thing they went with, but I fear in future he may become a broken record. While I'm not sure why they decided to make his love for food so apparent, it's a nice quirk that stops him from being completely one-dimensional. Since they made him so important to the story, I very much hope he stays likeable.