I just bought the latest (late 2013) 15" Retina MBP, quad core i7, 16GB RAM, 512GB SSD. The boot times, whilst certainly much quicker than my mid-2010 MBP, aren't as lightning-fast as others on here seem to suggest they should be. From the Apple logo onwards is very quick, but from cold up until that logo isn't especially quick. Again, it's not horrendous, but it's certainly not the "10 seconds" people keep talking about. For what it's worth I set the rMBP as vanilla/"new", i.e. not restored from a Time Machine backup.