The animation -- if we're talking about the "color splash" one -- is the same as before, about 150-200 ms.
Perhaps you mean the animation of the remaining message list item "sliding up"? This is a bit longer, I believe (it comes from someone else's library which I'm using), but also not quite 500 ms.
Anyway, please try updating to the latest "development" version from last night, 1.6.2.6-pre6, here on the forum in the "development builds" section:
- Has an optimization which makes the message list smoother
- When the app's overall "use animations" is OFF (as yours is, I believe), the "slide message list items up" (or "down to make room for a new message") animations are turned OFF too.