In a short period of time Sierra has earned a great deal of my respect, particularly for their across-the-board support for x64 (64 bit) versions of Windows. I first tried their AC881, service provided by AT&T, which worked perfectly, but I read the fine print, did the math and found that usage over 5GB/month was going to cost me $500/GB! And according to the card, I used ~4.8GB in 8 days!! Potential to run-up a 4-figure data bill lacked appeal to me on so many levels, that I closed that account and jumped to Sprint.
Now I'm using Sierra's AC 595, which works flawlessly as well, and I am more than pleased with it! More, I found Sierra's support staff highly responsive and very professional. (I only contacted them to inquire about x64 driver support for their products.)
So I'd say my expectations have been exceeded, and then some.
If you are running, or plan to upgrade to 64 bit Windows, then you'll want to be sure you choose a card made by Sierra!