FWIW, a lot of posts would seem to imply that the HD2 is "unique" in its tendency to have problems with UHS-1 cards. The fact is,
a lot of devices have issues with these "high performance" cards. Mostly when it comes to ROMming, but there are some phones and tablets that don't like UHS cards even when it comes to just plain storage (i.e., simply using the card to store photos, video, music, etc.). For example, I was using an SD-card ROM with my Nook HD+ tablet, booting the system from a Sandisk 16GB UHS1 "Ultra". Everything seemed to be working fine, and then after a few days things started to go wacky. A little digging on the forums indicated that other people were having problems with that card (which happens to be very popular). So I switched over to another non-UHS card, and sure enough, all my problems went away. So, one shouldn't think that this is somehow a limitation suffered only by the HD2, just because it's an older phone. As I've said, a lot of newer devices don't play nice with UHS either.
My own rule of thumb is that I don't use UHS-1 cards with ANY device, EXCEPT for digital photography equipment. (And for this specific application, I use them exclusively)
Cameras are designed to take advantage of the lofty sustained write speeds these cards offer, and clearly benefit from them. But I have seen virtually NO benefit to their use in phones or tablets, either for ROM use or for general storage. For these devices there is almost no upside to using them, and they often cause headaches (as the numerous forum posts will attest to).
Now, there is no shortage of people on the boards who hold strong opinions about what the best card is for ROM purposes, but for anyone who's interested I'll throw in my 2 cents: The Samsung Class 6 (in 16GB or 32GB capacity) has never let me down, either in speed or reliability. I managed to get my hands on one recently, and for those who are into numbers, here are Crystal Disk specs...
MicroSD - Samsung 32GB CL6
Tested on ASUSGARS, 2014-09-14, internal card reader
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CrystalDiskMark 3.0.2 x64 (C) 2007-2013 hiyohiyo
Crystal Dew World : http://crystalmark.info/
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* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]
Sequential Read : 19.296 MB/s
Sequential Write : 15.858 MB/s
Random Read 512KB : 18.993 MB/s
Random Write 512KB : 17.620 MB/s
Random Read 4KB (QD=1) : 4.089 MB/s [ 998.2 IOPS]
Random Write 4KB (QD=1) : 2.148 MB/s [ 524.3 IOPS]
Random Read 4KB (QD=32) : 4.272 MB/s [ 1043.1 IOPS]
Random Write 4KB (QD=32) : 2.055 MB/s [ 501.7 IOPS]
Test : 1000 MB [G: 0.0% (0.0/29.3 GB)] (x3)
Date : 2014/09/15 1:42:00
OS : Windows 7 Ultimate SP1 [6.1 Build 7601] (x64)
As you can see, the card is a monster. This is a Class 6, yet across the board it blows the doors off even most Class 10 cards. [It even out-classes my Sandisk 'Ultra' UHS1 card, in every metric except for
Sequential Read and 512KB Random Read] But most important, are the exceptional read/write speeds for 4KB file sizes. This is probably the most important metric when it comes to ROM performance, e.g., in Native-SD or Data on EXT scenarios. The only "problem" that exists with this card is that Samsung has discontinued production, so they've become harder and harder to find, and when they are available you usually have to pay up.
But if you should ever have an opportunity to purchase one (from a reputable source), DO NOT hesitate!