I was there!
Btw, yeah, I was kinda worried about the serve also. As at first she served very weak, but then she started adding more power. I kinda think this might be Venus trying one or two new things as in Luxembourg she said she was going more for percentage than power. So she might want to mix her serve more and she used this exhibition as an experiment.
Her ground-stroke games looked fine though, but still, too many errors
Btw, I dunno if it was aired or not, but after the match there was a talk-show by the court about Kim (this was between the singles and doubles match), and Venus was one of the guests. They both said nice things to each other, basically (and Clijsters mentioned Serena as well). Venus said she first noticed Clijsters when she was playing Serena in 3R of USO 1999 and was thinking: "Who is this girl trying to beat my sister?". Then Venus said about her last two encounters with Clijsters at the USO (2009 and 2010) and Clijsters ended up winning the title in both occassions. Clijsters (jokingly) said Venus was her good luck charm, then; and Venus answered Clijsters was her bad luck charm, lol. Then, Clijsters said because she is gone now so Venus can win the Open.
And I do hope she was really in exhibition-mode (like Serena) and let Clijsters have that win. This was her very last match anyway...