Unknowns: Sandisk vs ADATA SSD
The Zenbook Prime, both 128GB and 256GB models, ship with one of two very different SSDs. You either get a slow Sandisk U100 or fast ADATA XM11 which have the same capacity but dramatic differences in performance. The ASUS model numbers are exactly the same so there is no way to determine which model you have until you open it up.
I was one of the unlucky ones to get stuck with the Sandisk so I decided to run a few tests. Here is one result.
While still better (barely) than a mechanical hard drive in most circumstances, certain tests perform an order of magnitude worse than its ADATA counterpart.
For a more in-depth review of the differences take a look at the article linked below.
[ASUS Zenbook Prime SSD performance comparison: Sandisk vs ADATA]
Unknowns: 3517U vs 3517UE
Similar to the SSD confusion, ASUS has not gotten its marketing ducks in a row as far as the Core-i7 version is concerned. Some online merchants have a 3517U (1.9-3.0 GHz) listed while others have a 3517UE (1.7-2.8 GHz). Not a big deal but still unnerving that a customer cannot get a straight answer to what process will be in the laptop.
No dedicated home, end, pgup, pgdn row
The lack of this frustrated me at first but I quickly got used to the new location among the arrow keys.
Max 4GB of RAM
For a modern laptop 4 GB is the minimum that can be considered acceptable. For those of you that find it hard to see why this is the case try firing up a VM and look at your available memory, ouch. For most tasks this amount is more than adequate but far from future proof.
Touchpad
If you have read some of the other UX31A reviews you may wonder if the touchpad as bad as many say. The answer is both yes and no. In general it is perfectly acceptable but not noteworthy, but the gripes I have are small but numerous.
First off the cursor can randomly jump around while typing if you accidentally hit the large touchpad. This is a rare occurrence, but if if you use a mouse and it becomes a problem, thankfully you can easily disable the touchpad by pressing Fn+f9.
Secondly the cursor tends to move if you click on the extreme lower left or right corners of the integrated buttons. I have become accustomed to staying towards the center of the buttons now.
Finally there is no way to trigger the right and left touchpad buttons simultaneously. This is a bit frustrating if you have become accustomed to using them to paste text in Linux.
Most of these issues are small, and 99% of the time the touchpad works as expected.
You can’t upgrade the RAM or SDD
The UX31A cannot be upgraded. While this is not a revelation for an ultrabook, it is a shame if you are stuck with the lousy Sandisk SSD or want to upgrade the RAM. A quick inspection inside the case shows that the RAM is soldered into the motherboard, and the SSD has a proprietary connector which makes it incompatible with current mSATA SSD.
If you absolutely need more checkout the ASUS UX32VD which has the ability to upgrade, but it is also a bit larger and includes a discrete video card.