I installed the latest edition of flash + plugin, version 10.2, and my game was stuttery, major pauses with green slopes, and sometimes ball travells in slo-motion. It might have given me a more smooth meter (didn't keep it to long to find any skips), but the game became so un-enjoyable, it wasn't worth the sacrifice.
I uninstalled the latest flash plugin, and re-installed version 10.0.45, the version before 2 updates, and game was smooth again, appart from the odd meter skip.
I rather take the risk with meter skips than play the stuttery game you get with latest flash, so its not all down to WGT, just the fact they have to rely on an unreliable flash program.