The SanDisk Ultra microSDXC 128GB is perfect for users that desire huge storage capabilities and don't mind lower performance compared to other of SanDisk's microSD cards. The card to which we compared the Ultra microSDXC, the Extreme PLUS microSDXC, provides some perspective for the Ultra microSDXC. With the 128GB Ultra, the user effectively gives up about half of the performance speed for twice the capacity. Potential buyers should be not judge the Ultra microSDXC too harshly on performance though, the card will still accomplish all it is asked in the target use cases.
The biggest knock may be the current street price of roughly $200, which translates to a 4X price premium and only a 2X capacity boost when compared to SanDisk's 64GB Ultra microSD card. It is early though and pricing will fall more in line as production ramps. For those who have a serious need for the extra capacity, price is unlikely to be a deterrent anyway, there just simply isn't another single card solution for capacity strapped end users.
LG has mentioned that the latest LG phone support 2TB MicroSD Card support. This feature may be available only if any company designs such a memory card. Till then you have to use only 128GB card.