I have tested dozens of SDHC and micro-SDHC cards. One disturbing trend I noticed is that: the speed class rating for micro-SDHC is typically inflated. For example, a 'class-10' rating means the card must deliver a sequential write speed of at least 10MB/s. But somehow, a class-10 microSDHC cards is always slower than a class-10 SDHC card from the same manufacturer. Case in point: the PNY 32 GB microSDHC Card (P-SDU32G10-EFS2) claims to be 'class-10', yet it can only write at 8.6MB/s maximum, while the full-size PNY P-SDHC16G10 achieved 13.4MB/s according to CrystalDiskMark v3.01.This SanDisk Ultra 32 GB microSDHC Class 10 UHS-1 card (SDSDQUA-032G-U46A), however, proves to be the exception. It achieved a sequential write speed of over 10MB/s according to two different benchmark programs (11.8MB/s in "CrystalDiskMark", 10.6MB/s in "H2testw v1.4"). This is faster than all my other microSDHC cards, including two 'class-10' cards from PNY and Polaroid.A closer look at the file transfer speed using "Flash Memory Toolkit" revealed another nice surprise: For writing small files, this Sandisk Ultra microSDHC card performed just as well as its full-size counterpart, the SanDisk Ultra SDHC (SDSDU-032G-AFFP). In contrast, all my other class-10 microSDHC cards perform poorly while writing smaller files. See the benchmark results I uploaded to 'Customer Images' for details.When you use a memory card in a digital camera to record HD video, it needs to store a huge video file each session. That means its sequential write speed is most critical. When used in a tablet or a smart phone, however, the card's random write speed for small files is more important. That's why in such applications, the Sandisk microSDHC will perform faster than the PNY and Polaroid cards, even though they are also rated as 'class-10'.[Bottom Line]As of this writing, the Sandisk Ultra microSDHC card ia actually priced lower than other class-10 cards from PNY and Polaroid. This makes the Sandisk the best value - especially if you need honest class-10 performance across all platforms.[Side Notes]- Do not confuse this Sandisk Ultra card with SanDisk Mobile Ultra microSDHC (SDSDQY-032G-U46A). The latter is rated for class-6 only.- The size of this '32GB' card is 29.7GB according to my computer. This is actually normal because computer people count one Gig as "2 to the power 30", which is 7.3% larger than one billion. So 29.7GB translates to 31.9 billion bytes, which is '32GB' according to marketing people.[Update on Feb 4, 2013]1. Amazon combined the Sandisk Ultra 32GB and 64GB cards on the same product page. Please beware that your intended appliance must be compatible with 'SDXC' in order to used the 64GB version. My original review refers to the 32GB 'SDHC' version.2. There are two part numbers for the same card. If you start from the Amazon product page and select 'Retail Packaging', you'll see the part number of SDSDQUA-032G-U46A. But if you click on 'Frustration Free Package', the part number changes to SDSDQU-032G-AFFP-A.[Update on Oct 5, 2013]The Sandisk microSDHC card works great in my new Samsung Galaxy S3, without the need for reformat (the default format is FAT32)[Update on Dec 26, 2013]My old test results were limited by the card reader and USB 2.0 port used. I re-tested the Sandisk UHS1 micro card using the Transcend RDF5 Card Reader connected to an USB 3.0 port. Here are the results from 'CrystalDiskMark 3.01 x64':- Sequential Read speed = 40.0MB/s (was 34.8MB/s when connected to USB 2.0 port)- Sequential Write speed = 13.1MB/s (was 12.6MB/s when connected to USB 2.0 port)