My end result was the same as kahhoek.
But I did successfully update to 3.6.
In late May 2011, I updated to 3.6 and it worked fine until this August.
Then I went to turn the device on and it was completly dead.
I had used the device may times between that period and I know the battery was fully charged.

Below are the firmware steps I had done to get my 255W as a 465:

6/19/2010 - My 255W HWID 827 was flashed using 082701000640to465.rgn from acleite.

6/21/2010 - I used 255Was465update320.rgn from acleite.

1/16/2011 - Using the nuvi465T_340.exe from Garmin, I extracted it and copied the GUPDATE.GCD file within it to the Garmin directory of my SD card.
I installed the SD card into my nuvi 255W and turned it on.
The firmware loaded fine and the unit worked well.

5/27/2011 - Using the nuvi465T_360.exe from Garmin, I did the same as on 1/16/2011 above.

Like I originally said, 3.6 worked fine.... for about 2 months... but now its dead

As ddabcd277 said above, I think it can now only be used for parts...