[T-Mobile, Samsung Galaxy SIII] rayman2k1:
How to get the new baseband with Odin

Here is what I did because I hate Kies and the OTA wasn't rolled out to me yet (WIND). I am only interested in the baseband, but I'm sure that there are other changes that Samsung has made to the OS as well (I noticed Swype is now slightly better). However, I am of the firm opinion that TouchWiz is a pile of horse dung and will never use is as DD.

Also, I did flash back the original nandroid of my WIND ROM (you have one, don't you?). I am not sure whether this step is necessary, but it won't hurt.

STEP ZERO-1: Make a nandroid backup of your current config. Though this won't help much if you eff things up, it will give you something to go back to once you've successfully flashed the new baseband.

STEP ZERO-2: Install the Samsung USB drivers if you have not already. It it part of the S3 toolkit here and I'm sure it can also easily be found elsewhere.

I do highly recommend the Toolkit as it will make your life easier when/if you want to flash an unsecured boot image and root and install CWM Recovery after getting the new baseband.

First

, you need the update files, so use Check Fus web downloader. Download the tool from here (you want to click the link labelled Check Fus Downloader 2.1)

Open Check Fus Downloader 2.1 and from the main (Standard) tab, on the right hand, under Choose a firmware, select Android from the first drop-down, then SGH-T999V from the second drop-down (it's the last SGH-xx model on the list), then choose your carrier (region): GLW for WIND, MCT for Mobilicity, VTR for Videotron. Then, from the left hand side, click "Check firmware". Underneath, in the Result section you should see Latest firmware: T999VVLALH2/T999VYVLALH2/T999VVLLH2/T999VVLALH2. If you do, click Download.

Once it's downloaded, you'll have a zip file. Unzip the MD5 file that's in the archive and keep it handy.

Second

you want to download Odin 3 (the version shouldn't matter from what I understand, but I used the one that comes with the S3 Toolkit here.) If you have the toolkit, find where you installed it (default is C:\Samsung Galaxy S3 QCom ToolKit) and run Odin3_v3.07.exe

Now, without touching anything else, click PDA and find the MD5 file you extracted from the downloaded zip in the previous step. Now, you should have only three check marks: Auto Reboot; F. Reset Time; PDA (and obviously in front of PDA the MD5 file you pointed to should be there).

Third

, put your phone in Download Mode by turning it off, then pressing Volume Down + Home + Power Key (and holding until you see the "Warning!!" screen). Press Volume Up to continue. Now connect your phone to your computer and let the device be found and installed. Once it has, a change will happen under the ID:COM box in Odin (mine turns a light teal color and says 0:[COM9]). Now press start and go get rid of the brick you shat in your pants.

Like I hinted, you will lose root and everything low-level custom with it (though your OS will stay put, so programs should stay there too). So, you will need to flash an unsecured boot image, root, install busy box and install a custom recovery (again).

I've got this on now and I must say that the throughput on HSPA+ is excellent. I'm getting between 700-900kB/s (yes, Bytes) which is about 7Mbps. Not effing bad for the little mobile telco that could!