The local setup was quite usual: PostgreSQL 9.2, Mint 13, default conf in VirtualBox in iMac i5 12GB. (read: home computer, no tuning)
For me the result is that mostly RedShift is on par with local PostgreSQL, sometimes even winning for <5M rows. So with better PostgreSQL tuning you can probably stretch it, but not for as much as RedShift can do for REALLY big data.
Also the big deal was that RedShift scaled linearly.