The trailer was a little disjointed and unintelligible, but (other than the tentacle/window scene) it looked like some weird sentient zombie that throws hooks at people. Maybe the actual movie or later trailers will include, I don't know, a plot?
The comics with Venom were initially cool, but then he started to appear everywhere to milk his popularity in a way similar to what has been and still is being done with Wolverine. There was even a miniseries where (I think) the plot was that Venom is feeling repentant and goes on a spree solving crimes in an almost Batman fashion, but bloodier.
I did like the Maximum Carnage story arc though, in that one Carnage has like 10 baby symbiotes and they all go after Venom/Spidey so they have to team up to stop them. They all had their cute little names of course, none of which I can remember. :/
If anyone has read Earth X though, that's my favorite appearance of Venom. Peter Parker is in his mid-late 50s, totally out of shape (as the Thing put it, he was "bit by a radioactive spare tire") and he's arguing with his now adult daughter about her relationship choices. He can't believe she's bonding with the Venom symbiote.
Back to the original discussion, I agree that the casting choices seem bad. At first I didn't like Toby, but he proved himself pretty well I think, even if he isn't quite as rugged as the comic Parker of the 70s-present... early Parker looked like a total wimpy nerd, Toby nailed that. So we'll see what can be done with these new people.