Grand Theft Auto IV really brought a lot of amazing tech tech with it along with a seamless city really bustling with life. It was always pretty impressive to see random things that could happen just because gameplay systems combined in a specific way.
 
However with any complex gameplay systems, there is a greater likelihood of bugs. The PC version probably brought more of these to light than the consoles mainly because of the recording features. 
 
Evidence (this is hilarious):