I'm using:

Code:
Enable Game Source

Resolution: 1920 x 1080
Frame Rate: 29.97 FPS

Preset: Very Fast
Quality: 10
Max Bitrate: 2300 (kbps)
Buffer: 4792
Audio: 44,100 16-bit Stereo, AAC LC, 96,000 Bitrate.
I'm not saving the video, so don't really care about the compression, hence only 'Very Fast' on the Preset; I'd also like to 10-box without changing settings, so the relatively low CPU usage is great.
I've had the best results with a buffer twice that of the total Bit Rate.

Chances are, I could go with higher settings...
But the quality is great (all of my game text, or my iTunes playlist, is legible while streaming).
And having several torrents going, doesn't impact my stream.

For reference, I box with an i7, 3930K (OC @4.5GHz), 32GB 1600MHz CL8 Ram, GeForce 670 GTX 4GB, OCZ Vertex 3 120GB SSD x2 (in Raid 0).
My internet is: Shaw Broadband 250 (250Mbps Download, 15Mbps Upload).



I have three main scenes.

The first is the primary monitor only.
The second is the primary monitor, plus the slave regions along the bottom (scaled down)... as if I were boxing with all regions displayed and on one monitor; to be able to scale the slave windows down, I had to use screen region capture rather than game source for the Slave Windows.
The third is a non-broadcast screen, in my case the WHMIS sheet for the Element: Woman.

I generally run with Scene 1.
But do regularly get requests for the "boxing" view.