Viewers with due to respect I want to share my personal experience with windows 8.1, as a computer teacher I have to deal with various types of softwares hence I need a fast operating system I am using windows 7 professional since 6years and during this time period windows8.1 launched and I shifted to it and found my pc completely paralysed on my single fast commands, it is only due to addition of windows store which need much ram so I recommend if you have 2gb, 4g ram pcs laptops u go for windows 7 which need lesser ram.
and people having i3, i5, i7 pcs can easily use windows 8.1 without any lagging problem.