No offense, but I fear your problem is with your computer, not Lightroom. And I am no Lightroom fanboy, believe me.
As I type this, on an iMac, I also have a Dell running Windows 8.1 next to me. 16GB of ram on the PC, 32 on the Mac. I have about 57k raw files on the Mac, 40k on the PC. (Lately I have used two catalogs with each: one for "current year" photos, one for everything else. This just made sense to me, but there were no problems before.)
I have had absolutely no speed issues with Lightroom (or any other of my processing software, including Capture One, Iridium, PhotoNinja, DxO, and, of course, Photoshop.) I do admit to waiting for LR to render previews sometimes, but that is highest quality, 100%, and not really much of a wait. Seconds, not minutes. Nor are there issues with icons, screens etc.
I suggest you do a reinstall. Remember to remove all of the preferences, and anything related to LR in your system. Before reinstalling, use diagnostic software to check out your computer and see what the problem is. On a Mac OnyX is quite good, and free.
Good luck...