I added a 128gb card to my T100 (I have the early version from about 2 years ago i bought it).
It worked well-ish at first. Dropbox cant be run off it, so if i keep my dropbox files on it, then it doesnt work the same as when they are on the hard drive.
So instead i moved about 35gb of music onto it, but then every now and then Window media player couldnt play anything and i had to un plug and replug and re-locate the micro sd card for it to find them. Found that tedious, so i switched to VLC player instead but also got a problem with the tunes on the card so i gave up.
Also if things are stored on the micro SD then the search box on the laptop doesnt pick up on those files, which is a bit of a pain in the ****.
Im really happy the 4gb is out and although my files are less than 64gb, im concerned that windows and all the other crap is gonna take up loads of space and I also heard if you use up all your hard drive space, your laptop wont run well at all. Not sure if that applies to Solid state drives too though.