Nikon d3100 video auto focus?

I want to get a Nikon d3100 but I hear that the noise quality is not good. I'm wondering if it can record without the auto focus because the noise is annoying! Would the canon 550d be a better dslr camera?

Added (1). I just want a good entry level dslr not for professional use.

Who told you that the noise quality is not good?

Here is a shot taken with a Nikon D300 which scores lower than the D3100 under low light conditions.

This shot was taken using ISO 3200.

And not really

Have you ever tried to shoot video using a dSLR? You have to use the LCD to compose and focus your shots. NOT an easy thing to do.

Atuo-focus in the video mode is worth any little noise you may get in the process.

Have you seen a comparison of the video from a D3100 and 550D ($200 more expensive)?

Here is a video shot using both auto-focus and manual focus using a Nikon. With auto focus and manual focus

Noise wouldn't be a problem (at least compared to the T2i), not sure who told you that.
The only problem with the D3100 continuous auto focus is that it isn't very good or at least good in the sense one would expect (as with many HD video DSLRs due to the current limitation of the technology). Of course it is a function that the T2i does not have in case you do want to use it. Something to consider is that the D3100 does not have an external mic input and only does 24 fps 1080 vs 30 fps on the T2i and no 60fps 720p like on the T2i.