I second this!Windows 8.1 is amazingly fast and gives a smooth experience compared to Windows 7.
Boot time is like ~20 sec even on a very slow 5200rpm SATA and (i have heard) is about ~8sec for a SSD. I think the most important thing for a portable PC is the battery life and Windows 8 trumps Windows 7 by a huge margin in this category because of better management of resources. I get around 9-10h with a 6-cell battery.
I have been using Windows 8.1 since day one (when GA version was released). It' pretty fast and has no glitches.