Thank you! Thank you! Thank you!

You just breathed new life into my iMac 4,1 (upgraded to Core 2 Duo and a SSD).
I continue to be amazed how my 5+ year old machine continues to be a relative speed demon with minimal ongoing effort and cost. Your awesome little tool extends that even further.
Like I said -- Thank you!
I will make the firmware upgrade this weekend, and will report how it goes.
Just curious -- I also own a MacBook 1,1 that also has the 2GB limit and is not supported by Lion. I know that the Core Duo proc is not upgradable, but do you suppose that the firmware on it could also be upgraded to lift the memory limit and/or fool the Lion installer???
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Edit 09/10/2011
I am very pleased to report that my iMac is working perfectly post upgrade. Woot woot!
Some thoughts:
I first had tried running the tool while in Safe Mode, thinking that would be best to minimize any potential conflicts. But upon install and reboot no EFI upgrade was performed. Not sure why that is, but after performing the install again in regular boot mode, closing all open apps and disabling Little Snitch beforehand, upon reboot the firmware upgrade process kicked off as expected.
The machine booted to the desktop, and System Prefs now successfully reported it as a iMac5,1. However, both the network and the airport cards were no longer recognized (all other hardware looked okay). Luckily, performing another reboot solved this issue.
Just to be safe, at that point I used Kext Utility to clear the kextcache, and ran Applejack in SU mode to rebuild permissions and clear other caches. I also fired up Hardware Monitor -- all sensors and fans continued to be well within spec.
Everything seems to be working beautifully. There was an annoying bug with these machines that prevented the Mac Aluminum keyboard from working at startup and in SU mode, and now that is even fixed!
I have not yet tried purchasing or installing Lion, or installing 4gb of memory, but I only assume that those will work now without issue as well.
The only strange and new activity I see is a hidden volume called FirmwareSyncd getting automatically mounted and unmounted on occasion. Any idea what this is, and what it is doing?
Thanks again to MacEFIRom for providing a bloody brilliant tool to extend the life of our 1st gen Intel iMacs. Your time and talent in doing so is greatly appreciated!
And I'll sheepishly ask again -- Is there any hope in getting my Macbook1,1 Lion compatible as well? 
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Edit 09/19/2011
Today I was successful in installing 4GB of RAM, with System Profiler recognizing 4GB installed.
Still have not tried installing Lion, however more recent reports later in the thread make it seem like that may still be a challenge to do...

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Edit 10/02/2011
Confirmed that MAS still does not allow the purchase of Lion.
I assume that the (overpriced) retail copy of Lion (on the flash drive) would work.