One, all people happily using Windows 8 there are more issues than boot time. Microsoft store/account, DVD playing, and incompatible programs/old software.
Windows 8 has been around more or less 2 years, driver problems, and assorted aggravations should be past.
Two, I do not know about the Lenovo Y510. Some laptops, motherboard and/or BIOS,
only accept Windows 8 software/drivers. if Lenovo offers a downgrade option contact them about applicability.
There were HP and Dell refusing Windows 7, even from a new retail full install.
sidestep
Windows 8 OEM "mcrosoft has officially removed" hardware upgrade "rights" of Windows 7."
Three, major crime, is leaving XP Windows 8 seems a natural progression. Often a very frustrating experience. I have an older business laptop on Windows 8. Periodically, something easy in 7 is frustrating or impossible. May be I'll load Vista (have media and liscense).. But I wanted to use SSD.