The Idea of the device is that it sits flush in your macbook (the rMBP13 has a really short sd port), most cards stick way out there is a company called Nifty that makes the same thing but charges $40 and another TheMiniDrive is $30 for a capped adapter, this one looks nicer than both and is only $25 so I thought it would be worth checking out.
Also last Nifty I bought only worked for an hour
If no one has tried the new one maybe I'll buy one its not that much after all
Yes I realize that this product is "prettier".

But you are putting "prettiness" ahead of function…and you mentioned reliability of a previous setup only lasting an hour.
The reliability concern is due to things like USB sticks, SD cards, and micro SD cards are mostly made as storage devices that you put something on it & access it on an infrequent basis. I don't think that they are made to be rugged enough for continuous reading & writing that happens when we operate our computers.
These products being discussed are only adapters for micro SD cards. With the main "point of difference" being that they are flush & look pretty. These products are fine if someone just wants a portable method of storage for moving data or files from one device to another. But this may not be the best way to "add storage" to a single devices storage capacity.
Yes…the storage in retina MacBook Pro's is not easily upgradeable (technically it is not supposed to be upgradeable at all by the end user)…this is why rMBP's need to be configured with lots of storage up front. But…the website macsales.com does sell some storage upgrades…so you might want to check them out.
The other solution is…simply don't store everything on the computers internal storage. Off-load what isn't needed frequently onto some sort of external storage device…freeing up internal storage.
- Nick