I haven't played on the PC (or indeed posted in the forums here) for just under a year, but GTA V has pulled me back in like a beast its very good...I do rather suspect its a little GPU heavy for the higher resolution/glitzier image quality settings, but I would also surmise it would run on older hardware (anyone able to confirm that?). The minimum system requirements are:
OS: Windows 8.1 64 Bit, Windows 8 64 Bit, Windows 7 64 Bit Service Pack 1, Windows Vista 64 Bit Service Pack 2* (*NVIDIA video card recommended if running Vista OS)
Processor: Intel Core 2 Quad CPU Q6600 @ 2.40GHz (4 CPUs) / AMD Phenom 9850 Quad-Core Processor (4 CPUs) @ 2.5GHz
Memory: 4GB
Video Card: NVIDIA 9800 GT 1GB / AMD HD 4870 1GB (DX 10, 10.1, 11)
Sound Card: 100% DirectX 10 compatible
HDD Space: 65GB
DVD Drive
I bought it for PC from CJ's CD keys -
http://www.cjs-cdkeys.com/products/Grand-Theft-Auto-V-CD-Key-(Digital-Download).html