Ok, just updated my maps. A few notes from my experience to pass along. I backed up my old files. You should too.
1) There was no basemap.fbl in the iGo 2009.06 release, so I copied my old basemap.fbl into the new CONTENT\MAP directory. This may not have been necessary but I didn't try deleting it to see what might happen, yet.
2) I didn't rename any files, at all. All the old files were named USA_State.fbl, the new files are named USA_State83TA_2009.06_090710.fbl and iGo still recognized them. This is also true for the buildings, dem and poi directories.
3) I couldn't copy everything from MAP over, WinCE told me that I didn't have enough space. Rather than argue with an inanimate object, I deleted all poi, building, and map files for Hawaii, Canada, Mexico, Puerto Rico and the Virgin Islands. Consequences be damned! I might go back one day and re-add Canada in case I go visit, but in the present that is entirely unlikely.
4) I left the old Pioneer license in place (Pioneer_PNA_NA@0810_(PremPOI,_TMC,_LM)_2008-12-18_NN747.lic) and just copied the new license file ([email protected]) into the same directory.
5) I intentionally deleted each directory before copying the new one over. This way there would be no mistakes on the part of WinCE or myself of not overwriting the older map, poi etc. I also did the same with ezRider.exe; deleting the old before copying the new.
6) This was my first time using USB in WinCE mode so I had to take an extra step. Of course, boot into testmode from SD. Go into control panel, usbStatusSwitch, select "Mass Storage Device" and click "Change". Now plug in your USB memory stick and it should show up.