The Nexus 6 opened up for pre-order just a couple of hours ago, but either Google didn't expect a high demand and didn't prepare well for it, or the demand was much greater than anticipated, because the phone has already sold out.
The Nexus 6 has been quite controversial so far, mainly due to its large screen size. At 5.96" it's bigger than even Samsung's 5.7" Galaxy Note 4, and of course bigger than Apple's iPhone 6 Plus as well, although the difference in total size is smaller than you'd imagine. The nearly-6" Nexus 6 is only 1 mm taller than the 5.5" iPhone 6 Plus, but 4 mm wider. Width isn't usually the problem with "large phones," though, but height is, so if you're fine with an iPhone 6 Plus, you'll probably find Nexus 6's size acceptable.
Data shows that people use "phablets" or large smartphones much more than smaller phones, which makes sense, considering you have bigger screen real estate that you can use. Motorola also said at the launch of its new Moto G that most of its customers would prefer bigger screen sizes for their next-generation phones.
If you can live with the size, the Nexus 6 sounds compelling, despite its more "regular" flagship price of $650 for the 32 GB version, compared to the much cheaper $350 Nexus 5 before it.
The device comes with a cutting edge Snapdragon 805 (which is still based on the 32-bit ARMv7 architecture), 3 GB of RAM, 32 GB and 64 GB storage options (no microSD support, as usual with Nexus devices), a 6" screen with 1440p resolution and a 3220 mAh battery.
The rear camera has a 13MP sensor with OIS (Optical Image Stabilization), and it is supposed to be much better than on previous Nexus phones and potentially better than most other flagships, too. It uses the newer IMX214 Sony sensor (unlike the new Moto X that uses an older IMX135 sensor), but perhaps more importantly, it comes with Android 5.0 Lollipop which has much improved camera software and support for RAW files.
If you want to check out when it's available again for pre-order, you can try the Play Store, or you can wait until it's available in stores and on Motorola's site "in November". The Nexus 6 will also be available in 28 countries from Europe, Asia Pacific and North America later this year.