I hear a lot of critique about Dave's characterization, which I understand, but please keep in mind we only see him interact with John in the pilot and...well...given the not very subtle JohnDave fanservice that's included in the pilot, it wouldn't surprise me if this is just how he acts around John because...Yaoislop...? (This isn't me hating on JohnDave, or implying they'll become canon in the pilot, but I feel it's a rather likely and servicable explanation).
My main actual gripe with the characterization is John. The more frequent swearing (and not even the fact he swears, but the fact he DOESN'T use replacing words like "darn" and "crap" as he often does in the comic), and the bit about the postmaster and his fingers (which felt...really uncomfortable to be honest, but that is just my opinion), etc...it all just didn't feel very JOHN to me. I haven't seen very many people talk about this, so I'm guessing this is a rather unpopular opinion!
I think Jade and Rose were...servicable? They did their jobs and didn't feel especially OUT of character, but they seemed more like surface-level interpretations of their characters. This could, of course, be that they didn't have many lines, and also Vivzie's studios aren't exactly known for writing complex female characters... I'd simply have to see more of them to form a full opinion.
Actually, opposite to the complaints of too much swearing, I think Dave was a little too tame with his vulgar language? He doesn't really SWEAR too often (at least in comparison to Karkat and such) but when he does it's pretty creative and comes with equally creative rants. Also I noticed he said "Damn", like...a lot...and I felt that was weird? I don't think he ays it more than 15 times in the comic (from memory).
Anyways, I did enjoy the pilot quite a bit! It was really good! BUT it is a PILOT for a reason, so expect a lot of these points to change.
AHHHHHHHH