I use 8GB sdhc in my n770 (wsod'ed).
I removed card lock door, bypassed the card switch and pushed full SD-size to microSD converter.
It works ok. I use whole space on the card (ie downloading 7GB torrents via aria2c downloader).
What is quite strange. I used my n770 without any card for a while and I've got some reboot issues. Since I've put my new 8GB card - reboots dissapeared.
It's crucial not to make swap on the card in my device since if the torrent downloader takes more memory some heavy swapping occurs. Swapping and additional communication to the same card made my os freezed for some periods - the result was occasional 32k watchdog resets.
Of course I use Fanoush's sdhc enhanced kernel.