I have an 8GB SD card that I figured I can use in my GO 720 since it has such a limited memory of 2GB. the internal memory is however, enough for the for the 720's normal operation. There isn't really anything in the manual about the SD cars slot.
Is anybody using an additional SD card?
Is there a GB size limit.
What are you using it for?
I always run with an external 4GB. Having once upgraded to firmware 8.300, even though I have now backed up to 8.010, I could use 8GB if I wished to do so. So far, have not had a need for 8GB, though.
What's in my TT that uses the extra memory?
I keep the Euro map set as well as my regular N.A. map set. I visit Europe often enough to make it worth my while. Believe me, the TT's 2GB internal memory is stretched just keeping the N.A. set.
I keep a more substantial POI file than comes with the 720.
I keep my own POI file of all geocaches in the immediate area (usually around 2000 of them) along with HTML files (yes, the TT has a mini-browser) with all of their descriptive and recent log information.
I've been known to keep a movie or two on it for longer trips (see MobilNova 3rd party application - works on firmware pre-8.300).