I recalled last night that under Ubuntu 10.04.1 I had solved some video issues that showed up after updating by reinstalling whichever player I was using, and decided to experiment with that approach today. It appears to still be needed.
Best results so far involve removing VLC, smplayer, and gnome-mplayer and reinstalling smplayer. (Note that this cannot be a controlled experiment because I cannot easily restore the initial conditions for various combinations of players and the post-update state.) Rebooting variously occurred during the period of the experiments, but was probably not needed. With just smplayer (and totem that I didn't mess with) residual hesitation is barely at the threshold of perception. This removal and reinstall also fixes totem hesitation (I have no idea why). If VLC is also reinstalled, it shows very slight hesitation after the install, whereas it was significant at the time of post 1. With both smplayer and VLC, the smplayer hesitation may be slightly greater than without VLC, but this judgement is too sensitive to error to treat at fact. Hesitation with VLC player alone seemed to be slightly more perceptable than with smplayer alone. Either, however, or the combination, is much, much better than before.
Desktop 1: DFI Lanparty UT nF4 SLI-D/AMD Athlon 64 San Diego 2.2 GHz/G.SKILL 1GB x 2 DDR 3200/BFG GeForce 7800 GT/Ubuntu10.04
Desktop 2: Gigabyte 770T-USB3/AMD Phenom II X4 965 3.4 GHz/s. Talent 2GB x 2 DDR3 1333/EVGA GeForce 9800 GT/Mint 14 Cinn-lowlat