Bottom line is.....bullshit aside, the stock wheels nowadays are very light. Sure the BST's or forged mag are lighter, but you only really need to buy a pair when you want or need a 2nd pair of wheels for the race track.
There's fuck all difference in lap times between a BST and a forged wheel. Just like 748R says. The lighter wheel will let the bike tip into the turn a fraction easier, but once in the turn.....things are much the same.
As far as feeling a performance difference on the road......forget it.
However, if you are going to the shops to buy some milk, then the BST's would be a nice conversation starter.