How is it not working? what are the symptoms?

Is this what you're experiencing:
Press the 3 button recover mode and the phone will restart. It will show the I9000 yada yada screen (in white text) and then it goes blank- after a few seconds the boot animation comes out and the phone starts normally?

If you're experiencing the above then it maybe because you did no let go the 3 buttons (specifically the home button) fast enough once the I9000 screen comes up- you see in recovery mode the home button is to select an item highlighted in the recovery menu. The first item is 'reboot' so if you dont let go fast enough this will be selected and the phone will just reboot normally. If this is indeed the issue you're facing then next time you do a 3 button restart, very quickly release the buttons once it restarts.

Hope this helps.