The 820 is supposed to hit markets worldwide near the end of September, though the price will likely vary by region. (I'm guessing it will be similar to the 816, which is currently selling in the neighborhood of $350 in the US.) As it's replacing the aforementioned phone, the 820 comes with a few key performance improvements.
First, it gets a boost from a 1.5GHz quad-core Snapdragon 400 to an octa-core Snapdragon 615 with 64-bit support and big.LITTLE architecture. In English, 64-bit support should be helpful when you're playing games or using processor-heavy apps because it can perform better and won't drain the battery as fast; regular apps should see a small improvement in executing operations as well. Of course, these improvements will be virtually nonexistent until Google officially releases its next version of Android, which will come with OS support for 64-bit, and developers push ahead with apps that are optimized for the extra bits. (HTC confirmed that the 820 is going to updated to Android L at some point.) As for big.LITTLE? This means that the 820 comes with a set of four 1.5GHz cores for more intense tasks, as well as a set of four 1GHz cores for the everyday stuff that doesn't require a lot of processing power; this is done to improve battery efficiency.
The 820 retains the look of the previous Desire flagship, complete with BoomSound and the same solid polycarbonate shell. Unfortunately, it appears that the 820 comes with the same frustrating 13MP rear-facing camera, which our Richard Lai wasn't pleased with in his review. We hope HTC is using a different module or tweaked software that offers better performance. That said, the front-facing camera has stepped up to a not-shabby-at-all 8MP sensor -- yes, selfie cameras are all the rage these days -- and at least you'll get twice the storage capacity (16GB instead of 8GB) and an extra half-gig of RAM (2GB over 1.5). The battery hasn't changed at 2,600mAh and you'll have the same 5.5-inch 720p display.
HTC is also boasting that the device comes in a slimmer profile (at 7.74mm) and what HTC is calling "double-shot," which is a multi-tone unibody design technique that the company claims brings improved build quality and tolerances to daily stress.
I wasn't too surprised to discover that the 820's in-hand experience is incredibly similar to the 816 that came before it. The 5.5-inch frame isn't going to be a comfortable fit for everyone, but if you're used to palming large-screened smartphones, you'll likely find it tolerable to hold the 820. All but one of the colors offered are glossy -- tuxedo gray is the only matte option -- so the polycarbonate build is very smooth; however, this makes it more of a target for unsightly fingerprints. The SIM cards and microSD slot are tucked away under a plastic tab on the left side, while the power button and volume rocker are on the right. While the Desire features a lovely design, the camera unfortunately interrupts things a bit; it stands slightly above the rest of the back and is so close to the top of the device that, when looking at the sides, it's painfully prominent.