In my opinion, Tessa Thompson is a pretty good actress, even though I have only seen her on the wonderful cult hit UPN show 'Veronica Mars'. Her lines are (for the most part) well delivered and believable, even though sometimes her performance seems a little sloppy and unbelievable.
However, I have seen much better actresses in the past, it seems that Tess Thompson does not have much experience. Hopefully in the future, she'll be more experienced and a much better actress. I looked at her IMDB profile, and I also found out she's in the big motion picture "When A Stranger Calls", which looks very entertaining.