What can I say, Nice Card works well in my Garmin Nuvi 760.
I see some bad reviews on SDHD cards this is because it is a new format, not all SD Card readers can see SD HD, even though they are physically identical. This includes new devices being sold here, read the device instructions / specifications first then place your order to make sure it will support the card, and don't be too surprised if you have an existing bit of kit that won't see it. If you have any doubts buy a 2Gb SD card as most SDHD readers are backwards compatible and will see it.
In the case of Garmin check out the website FAQ this is the only place where it says max size is 4GB SDHD.