Pro Main heat source is off to the side
Although Asus allows the laptop processor to get pretty hot, they intelligently designed the laptop so the heat source would be in the top right corner, away from where you are normally typing, however if you have the laptop on your lap, it can still get hot.
Pro Runs silent and cool with no fan
The Asus UX305 uses a low voltage Core-M processor which runs cool allowing the laptop to not require a fan while still running cool. This makes it safe to use on your lap or in bed without burning yourself, or having to worry about the computer overheating and getting damaged.
While it's cool for general use, very intense use could still lead to it getting hot.
Pro Great specs for the price
Most laptops in this price range make larger sacrifices, but the Zenbook UX305 has a 1080p screen (upgradable to 1800p in the $999 model), 8GB of ram, a 256GB SSD (upgradable to 512GB in the $849 model), and 9-10 hours of battery life. Even with these specs, the base model is only $699.
Other laptops in this price range tend to have some compromises, either a 1366 x 768 screen, or 4GB of ram, under 256GB SSD, or poor battery life.
Con Lip of screen lid comes below rubber feet when open
The Asus UX305 has a design flaw when the lid is open, letting the bottom of the lid underhang pushing the back of the computer up a bit, making the back rubber feet not touch the table. Because of this the laptop can slide around a bit on a table.
Con Mid range performance
While the Core-M processor has the perks of low power consumption and low heat production, it's not going to be a powerhouse. You should be able to run chrome with many tabs, video, photoshop, virtual machines, and most non intensive work related functions without any hiccups, but don't expect to run most games smoothly.
Netflix and YouTube will run fine, but some streaming services, like HBO will stutter.
In benchmark tests, it rates around the level of the 2014 Macbook 13" Air, but lags behind in single threaded applications.
A game like skyrim runs slowly with occasional crashes, while games like League of Legends can get 60fps on very low setting, or 45fps on low.