There have been some questions regarding going to FRF83 from FRF72...
You have 2 options for putting FRF83 onto your phone if you have FRF72
a) Wait for an official OTA update
b) Use the PASSIMG method to get back to STOCK 2.1 then FRF50

Notes:
  • I am not responsible for what happens to your phone
  • This will wipe all data, please back up your stuff
  • It's all STOCK stuff, so... not rooted
  • I did this one my T-mo (AWS) N1 only

If you can't wait for an official OTA update, you can do the following...
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For the PASSIMG method to get back to STOCK 2.1:
  1. Get the stock shipping ROM.
  2. Rename file to PASSIMG.zip
  3. Format SD card and Factory Reset your N1
  4. Power Down your phone
  5. Pop out the SD card and put PASSIMG.zip on it
  6. Put the SD card into your phone
  7. Hold Vol Down + Press Power
  8. Bootloader will read passimg
  9. Follow instructions to flash phone
  10. When complete, you will be back at ERD79 (The shipping ROM)

Incremental Updates:
Get ERE27 from ERD79 ROM
  1. Power Down your phone
  2. Pop out the SD card and put rom on it and rename it to update.zip
  3. Put the SD card into your phone
  4. Hold Vol Down + Press Power
  5. Press Vol Down until RECOVERY is highlighted
  6. Press Power
  7. Wait for Android "!" screen
  8. Press Power + Vol Up
  9. Select Apply:update.zip
  10. Reboot when complete

Rinse and repeat Incremental Updates steps with the following ROMs:
FRF50 from ERE27
FRF83 from FRF50

You might also want to wipe data and cache when you get to FRF83 just so you have a fresh start.

I'll see if I can find links to the roms...
GL

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Oh yeah, I noticed that booting and shutting down was slow and the live wallpaper was laggy when I was on the 2.1 ROM, I think I have been spoiled running froyo since the first FRF50 hit. :-p