Recs.
Updated
LG did a total hardware re-haul with the G5. This is their first aluminum phone, and is the first phone with a modular slot. They also shrunk it down a bit to make it easier to hold.
Specs
Pros
Pro Rear camera captures more scenery
There are 2 rear cameras on the LG G5 - a primary (regular style) 16MP camera, and a secondary wide-angle 8MP lens. This dual-setup allows for a few things - using the 8MP camera you'll be able to fit a whole lot more into the frame, and the 16MP camera is better at focusing on a certain point with crazy detail. Also, there's a feature where you'll be able to use both cameras and stitch the images together. This will create a high resolution mid-section to images, but still include much more in the frame than any other phone camera would allow.
Pro Modular bottom port
The bottom of the G5 can be removed, which allows access to the removable battery. You can also change out the physical connector to add different modules. Currently there are two replacement bottom ports that add modular functionality. The first (and arguably more exciting) is the camera grip. It adds a zoom wheel, shutter button and dedicated video buttons, as well as a secondary battery (1100mAh). The second is a high-end Bang & Olufsen module which will allow for Hi-Fi audio output through the embedded headphone jack. This will allow for higher quality 32-bit audio output.
Pro First device with Snapdragon 820 CPU
The LG G5 is the first Android device to use the high power Snapdragon 820 CPU, which means very high end performance. It is ever so slightly beaten by the Exynos 8890 in computing power, however the Snapdragon 820 offers a better GPU which leads to better in-game performance.
Pro Unique feeling metal casing
The metal used for the case of the phone is created by LG themselves in a fashion that is still unknown that they are calling microdizing, but it does make for something that feels a bit different. It also allows for the antenna to be used without needing slits in the back of the casing, a first for smartphones.
Cons
Con Poor battery life
The battery capacity is a bit small at 2700mAh, and it has a strange idle battery drain (up to 20% of the battery can be devoted just to 'idle' each day - perhaps the always-on display is included here instead of the screen battery stats). Most users will need to charge the battery, or swap out batteries thanks to its removable slot.
When the screen is on 100% brightness looping a video for 90 minutes, it only drops by 9% battery which is very impressive. GSMArena rates the battery at 60h, which is about average.
Con The missing B&O module in the U.S.
Worldwide there will be a modular attachment branded Bang & Olufsen that will allow Hi-Fi audio through a secondary headphone jack, however this won't be available in America,
Con New charging port
USB-Type C is the next standard which is starting to phase in - it allows for faster data transfers, and is reversible and more durable than the current Micro USB standard. It's a con right now because it's just emerging - it isn't compatible with many devices yet. As it becomes more common, it will start to become a pro.