hashcat VS aircrack-ng (Intel GPU)
My System:
Win7 Pro wSP1 x64 en-US
Intel i5-3570K Ivy Bridge

After I managed getting hashcat to work (copied *.cl files to main folder), I tried both hashcat 3.00 x64 and aircrack-ng 1.2 RC4 (not at the same time, of course), on the same cap/hccap file using the same wordlist.

hashcat v3.00 x64, using the Intel HD 4000 GPU, can manage ~3600 keys/sec.
aircrack-ng-avx v1.2 rc4 x64, using the quad-core CPU, can manage ~6000 keys/sec.

I thought using the hashcat with the GPU would give me much better speed. 

Has any of you guys got similar results, or is something awfully wrong with my system?
Nah, Intel GPU are bad, while Intel CPU are good. A good GPU like my 1080 makes ~400000 keys/sec.
wow...400,000 !
That's quick.