
Average Reviews:

(More customer reviews)tl;dr
Pros: Teeny-tiny, Fast transfer of big files, Holds card securely
Cons: Might be hard to remove card, Too slow for apps, Weird heat problems
Firstly, when I was shopping around for this reader, I did not actually understand how small it would be. The round part is literally smaller than a dime. This was never a problem, because the key-chain attachment is sturdy and I have yet to misplace it.
Some reviewers on other pages have had trouble with the item splitting along the plastic divide when pulliing the reader out of a port, but I haven't encountered this problem. My MobileMate was a little tight in the USB port, but with a little regular use that became much less of a problem.
The reader accepts MicroSD and MicroSDHC with no trouble. I haven't tried an M2 card, but I don't forsee any problem with it. The MicroSD cards fit all the way into the protective area, with only a bit of the face and the removal tab showing. They are held in snugly enough that I am unworried carrying the reader around with one in it at all times, but are still easy to remove, provided you have a bit of fingernail.
I only have two complaints/concerns with this product.
My concern is that, when left in a USB port and used for any fair amount of time, the MobileMate gets very hot. I've yet to have it melt or anything, but it makes me worry.
My complaint is more of a misjudgment on my part. I'd ordered this reader and a MicroSDHC card in lieu of a flash drive, because I thought it would be neat to have something so small. Now, while this reader and MicroSD cards in general have a phenomenal transfer rate with larger files, the performance drops like a rock when transferring a lot of very small files (like, say, if you were trying to run Portable Firefox).
With the heat issue and the lag I get on Portable Apps, I've basically decided to keep my MobileMate and cards for large data transfers and cellphone data stuff, not to mention that it's just a cool thing to have around. Plus the BlueProton deals with MicroSD cards (if they're still around) are excellent. But I'm buying a OCZ 4GB Rally 2 USB 2.0 Flash Drive (OCZUSBR2DC-4GB) for portable stuff.
Click Here to see more reviews about:
Sandisk Mobile ULTRA MicroMate microSDHC & M2 USB 2.0 Card Reader Grey (SDDR-121-GREY, Static Pack)Moving music, video, photos and personal data between your mobile phone and your PC is fast and convenient with SanDisk's compact MobileMate Micro Memory Card Readers. Designed to compliment memory-enabled mobile phone users, flash memory cards can be plugged directly into the readers for fast file movement between your phone and your PC. Direct plug in means no card adapters are required. The Ultra MobileMate Micro Reader is so compact; it can attach to your phone with the included phone lanyard or carry in your pocket. Designed for Class 6 & High Speed cards : MicroSD, MicroSDHC, M2 (Memory Stick Micro)

Click here for more information about Sandisk Mobile ULTRA MicroMate microSDHC & M2 USB 2.0 Card Reader Grey (SDDR-121-GREY, Static Pack)