I've been filming several interviews in a studio with the mic plugged in directly into the T2i and have been very satisfied with the results. I recently took it on the street for some OTS interviews and the sound would randomly cut in and out. Is this the AGC function everyone is complaining about?

If you mean by that what is described as pumping, where AGC kicks in to raise the gain when nothing much is happening, resulting in background noise being heard at loud volumes, then yes.

But the way you phrase it, cutting in and out, it doesn't sound like AGC. Can you be more specific?

Out on the streets, when the wind started to blow the sound would cut off. I've never experienced that before. That is why I was wondering if that was due to the AGC function.

Yes. The wind "scraping" across the mic holes can be a loud enough noise and the AGC cuts the recording gain suddenly. Two ways to try to get around this are the use of an external mic with furry windmuff (will help but may not completely eliminate "pumping") or the use of an external audio recorder like the ZoomH2 or ZoomH4n (both also with furry windmuff - available from thewindcutter.com).

I actually often use both at once, the Rode SVM with "Deadcat" windmuff on the camera plugged into the mic input and my ZoomH2 with windmuff on a stand out in front of the cam and as close to the talent as I can get it without it showing in the picture.

The camera audio is mainly for synchronization when I position the WAV audio from the ZoomH2 on a separate audio track in the editing package. I synch on the command "Action" for each scene by aligning the waveforms. When it's right and sync looks good I mute the camera audio and trim each scene where I need for "in" and "out" points.

The camera audio can also be a "backup" in case the Zoom audio went south.

For good audio you almost have to use an external audio recorder with these DSLRs.