Does the command make any visible changes? Do "impact effects" look different?

should probably do multiple benchmarks and find an average.

cl_new_impact_effects defaults to 0 for me and changing it to 1 had about a 10 to 15 fps decrease for me on average. Maybe it will help others out though.

Only thing I've really noticed is that the bullet impact looks different. There's probably others that I am missing though.

i use _surfacepropeties.vpk from Clean TF2, so i can't see any difference just because i can't see bullet impacts

from wiki:
If cl_new_impact_effects is set to '1', Source Engine's updated, threaded particle system (as opposed to the original engine's system) will be used to render bullet impact effects.

So it might be unstable for not multi-cores.

So here are the benchmarks
Note: For this benchmark i use ORIGINAL (means w/o changes) Comanglia's CFG

Original one
2639 frames 32.802 seconds 80.45 fps (12.43 ms/f) 5.517 fps variability

With cl_new_impact_effects 1
2639 frames 32.746 seconds 80.59 fps (12.41 ms/f) 5.600 fps variability

Does 0.1 FPS count? :D
I swear, i had these results above
Maybe i should try later, lol.

BTW. I edited this config and I have slight fps boost from my settings.
2639 frames 32.313 seconds 81.67 fps (12.24 ms/f) 5.673 fps variability

Idunno, just wanted to show off.

My shitty specs.
Intel Core i5 Quad-core
Intel HD Graphics
Craptop

There's a difference of like 1 FPS between your two benchmarks.
That's well within the margin of error for this test. The results change slightly every time you run the benchmark.
Same for me: cl_new_impact_effects 0 = 170FPS, cl_new_impact_effects 1 = 169 FPS.
Next time I did the test it was the other way round.
Tested once more ant the results where exactly the same...

Maybe it could have an actual effect when your GPU is the bottleneck.
But you'd probably have to have a integrated GPU for it to be your bottleneck in TF2.
In general there's a lot of graphic settings that don't really change FPS because TF2 is so CPU heavy while most modern GPUs don't even reach 50% usage.
Like I can set my shader, model and texture details to low or to high/very high and it won't change my FPS one bit.
And my GPU isn't even high-end by any means (GTX750Ti).

Where can I get that _surfacepropeties.vpk thing and whats clean tf2?

Where can I get that _surfacepropeties.vpk thing and whats clean tf2?

So what are those commands you changed in comaglias config to get the FPS boost?

http://pastebin.com/SrrKxi4N the whole config unstable for not quad-core.

http://www.teamfortress.tv/21756/prism-hud-clean-tf2