It does work. You are making a mistake somewhere along the line.
1. start ftp from your xmb
2. using filezilla on the pc connect to your ps3 and navigate to the mw2 folder (blus30377 I think it is)
3. in USERDIR there will be a file called patch_mp.ff, delete this file
4. upload the modified patch_mp.ff from this thread, to the same directory you deleted the original patch_mp.ff file. Make sure it is named "patch_mp.ff" exactly as shown or it won't work.
5. disconnect filezilla
6. press "x" on the ps3 controller to exit ftp
7. start mw2 and go online or private match
8. make sure "button layout configuration" option is set to "default"
9. enjoy the menu!