It may or may not be Vavoom. Does it happen with the other games as well (Doom, Heretic, Hexen)?
I haven't used the latest version of Vavoom, but these are some things you can try checking:
Anti-aliasing and interpolation options, both in Vavoom and in the Windows graphics card control panel. Also, hardware vs software rendering will sometimes give you differences, as well as using DirectX vs non-DirectX rendering.
I can try checking later and see how it looks on my end.
What are you using to play (OS, computer type, graphics card)?