The current texture streaming is good for an in development game, but currently doesn't account for textures/particles that will immediately appear in your face. (Such as bullets, or zombie flames in Virus, and the bullet projectiles in Planet Panic.) So what ends up happening on a low-mid range pc like mine is a consistent stuttering effect whenever the textures exampled above are to suddenly appear on my screen. (Note: The FPS animations of the guns and ships don't cause any lag and run fine.)
A simple fix to this would be to have these textures loaded at all times while playing these game modes, so that they don't need to be rendered when they immediately appear out of the gun. (Another fix for Planet Panic would be to not make the balls projectiles, that really kills my fps.)
I play around 40 fps with max settings, and I can't turn them down very much because of my poor CPU but decent GPU, (i7 860 @ 2.8ghz CPU, and geforce gtx 750ti GPU). (Should also be noted that my power supply is also poor and I suspect my hard drive is failing, but this is the system I play on.)
BallRace and Minigolf play at a smooth consistent fps depending on optimization of map, but they never stutter at the rate that Virus and Planet Panic do.
If this is actually not the problem and I'm rambling on the basis of a low-end, dying PC. I'd love to hear what is currently happening with the texture streaming.
EDIT: I didn't touch on the Plaza or Little Crusaders. Frankly I can hardly traverse the Plaza, and Little Crusaders runs at a remarkable 100+ fps with absolutely no stuttering.