Is this build good?

Solution
Here are the changes I would make. Crucial M550 is faster and is on sale. Added an aftermarket cooler. Changed the ram to a less expensive kit, that will work with the cooler. It will be tight, but it will fit. The Wifi adapter, I chose, is an Intel based one, with bluetooth. MSI graphics cards tend to be of better quality than Gigabyte. The MSI Twin Frozr is also one of the coolest running 970's.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($219.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($30.99 @ SuperBiiz)
Motherboard: MSI Z97-GAMING 5 ATX LGA1150 Motherboard...
Looks good... but you don't have a huge amount of storage space. If you're planning on using this as a gaming rig for only a few games, you're fine. Otherwise, get another drive (HDD 7200 rpm - WD brand) to store the games.
 
You have a good build going there!

CPU Cooler - Don't forget one.
MB - The Gigabyte below offers the same features at a lesser cost.
MEM - Expensive! Same specs on the modules below...

Enjoy that rig!

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($224.99 @ NCIX US)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($34.99 @ Amazon)
Motherboard: Gigabyte GA-Z97X-SLI ATX LGA1150 Motherboard ($126.98 @ Newegg)
Memory: G.Skill Ripjaws Series 8GB (2 x 4GB) DDR3-1600 Memory ($62.99 @ Newegg)
Storage: Crucial MX100 256GB 2.5" Solid State Drive ($105.03 @ Amazon)
Video Card: Gigabyte GeForce GTX 970 4GB WINDFORCE 3X Video Card ($339.99 @ Amazon)
Case: Phanteks Enthoo Pro ATX Full Tower Case ($99.99 @ Amazon)
Power Supply: SeaSonic 620W 80+ Bronze Certified Fully-Modular ATX Power Supply ($54.99 @ Amazon)
Wireless Network Adapter: TP-Link TL-WDN4800 802.11a/b/g/n PCI-Express x1 Wi-Fi Adapter ($36.96 @ Amazon)
Total: $1086.91
 


He has a 1TB hard drive from his old build.

 
PCPartPicker part list: http://pcpartpicker.com/p/GLh4wP
Price breakdown by merchant: http://pcpartpicker.com/p/GLh4wP/by_merchant/

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($219.99 @ SuperBiiz)
CPU Cooler: Noctua NH-D14 65.0 CFM CPU Cooler ($77.99 @ Newegg)
Motherboard: Asus Z97-A ATX LGA1150 Motherboard ($129.99 @ Amazon)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory ($79.99 @ Newegg)
Storage: Samsung 840 EVO 120GB 2.5" Solid State Drive ($72.99 @ NCIX US)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($78.99 @ SuperBiiz)
Video Card: Asus Radeon R9 280X 3GB DirectCU II Video Card ($249.99 @ Newegg)
Case: Fractal Design Define R4 w/Window (Black Pearl) ATX Mid Tower Case ($79.99 @ Newegg)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply ($52.99 @ SuperBiiz)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.99 @ Newegg)
Operating System: Microsoft Windows 8.1 - 64-bit (OEM) (64-bit) ($92.00 @ B&H)
Total: $1140.90
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-01-07 10:20 EST-0500

 
Here are the changes I would make. Crucial M550 is faster and is on sale. Added an aftermarket cooler. Changed the ram to a less expensive kit, that will work with the cooler. It will be tight, but it will fit. The Wifi adapter, I chose, is an Intel based one, with bluetooth. MSI graphics cards tend to be of better quality than Gigabyte. The MSI Twin Frozr is also one of the coolest running 970's.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($219.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($30.99 @ SuperBiiz)
Motherboard: MSI Z97-GAMING 5 ATX LGA1150 Motherboard ($146.98 @ OutletPC)
Memory: G.Skill Ripjaws Series 8GB (2 x 4GB) DDR3-1600 Memory ($62.99 @ Newegg)
Storage: Crucial M550 256GB 2.5" Solid State Drive ($89.99 @ Amazon)
Video Card: MSI GeForce GTX 970 4GB Twin Frozr V Video Card ($348.99 @ NCIX US)
Case: Phanteks Enthoo Pro ATX Full Tower Case ($99.99 @ Amazon)
Power Supply: SeaSonic 620W 80+ Bronze Certified Fully-Modular ATX Power Supply ($54.99 @ Amazon)
Wireless Network Adapter: Gigabyte GC-WB867D-I 802.11a/b/g/n/ac PCI-Express x1 Wi-Fi Adapter ($29.98 @ OutletPC)
Total: $1084.89
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-01-07 10:21 EST-0500
 
Solution
I'd upgrade PSU to 750W in case he wants to add a second 970 in the future. And, switch to cheaper but better RAM.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($219.99 @ SuperBiiz)
Motherboard: MSI Z97-GAMING 5 ATX LGA1150 Motherboard ($146.98 @ OutletPC)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-2133 Memory ($76.99 @ Newegg)
Storage: Crucial MX100 256GB 2.5" Solid State Drive ($104.99 @ SuperBiiz)
Video Card: Gigabyte GeForce GTX 970 4GB WINDFORCE 3X Video Card ($339.99 @ Amazon)
Case: Phanteks Enthoo Pro ATX Full Tower Case ($99.99 @ Amazon)
Power Supply: Rosewill Hive 750W 80+ Bronze Certified Semi-Modular ATX Power Supply ($79.98 @ OutletPC)
Wireless Network Adapter: TP-Link TL-WDN4800 802.11a/b/g/n PCI-Express x1 Wi-Fi Adapter ($36.95 @ OutletPC)
Total: $1105.86