Pros: 10 gigabit networking Plenty of fan headers
Cons: You cannot use the third m.2 slot for RAID. In the manual and on the product page they have a video showing triple m.2 RAID but those were taken with their z270 board. For some reason they did not implement the feature on x299. I have contacted support and they said this was working as intended so don't expect a BIOs update to fix it.
Overall Review: I would like proper m.2 support but there are no other options for built-in 10 gig currently and the board is priced pretty well even for 2x m.2
Pros: For the price works well, I have it paired with a 9600k so no power issues. I have the 9600k at 5 GHz with this board. Also applies the XMP profile with no issues.
Cons: ASRock BIOs is a little tricky to navigate but not bad once you're used to it.
Overall Review: With a 9700k or 9900k and overclocking you may need a more expensive board to handle the power requirements. The mATX version may be better for you if you want the option of using smaller cases This review for ASRock review rebate program