A1: AFAIK, this is totally normal on Windows8. Seems to me everybody is having similar issue on wifi connection with Windows8 unless your router is right next to you. When I'm in US, i didn't have this problem and my wifi router is right next to my laptop... My phone, tablet and Win7 laptop doesn't seem to have any problem at all.
A2: It doesn't seems to be related to laptop models.
A3: All I know is that any wifi card (except the one that comes with Intel chipsets) will be affected. I do heard Intel wifi cards do affected as well but I can't confirm. I'm getting a new laptop with Intel wifi card on win8 for works in next few weeks (or probably months... we'll see) so maybe I can confirm that later on.
A4: Some say the problem does goes away with Win7 drivers. So maybe you want to check Lenovo's website on that. I dont know if there's any.

for the time being, I just use LAN instead of Wifi...

nonsense le... i dont hv any issues at all.. my router is one floor below mine. tried multiple routers at frens place and public wifi.. no issues whatsoever.. wats the point of having wifi option and still get connected via cables..... mobility is gone...