A big part of how much faster LTE is than HSPA+ (which the Nexus 4 ships with), is the fact that most LTE networks are massively under-utilised. HSPA+ can run

A big part of how much faster LTE is than HSPA+ (which the Nexus 4 ships with), is the fact that most LTE networks are massively under-utilised. HSPA+ can run at 42Mbps in theory, but network congestion makes that a pretty much impossible situation in reality. As more people join the LTE networks, they will get slower and slower, just as 3G has in crowded areas.