SHAB, in my honest opinion, that was a big mistake dude...
If we're talking about the sportline grips, well, let me just say after 5 months of use i'm going to swap 'em for something else.
Never had any cramps/numbness/pain with grips in general but the Rizoma ones is the typical case of "form over function" :
1) i'm having pains in the palm area due to them since i have to grip them pretty hard since they're so thin in diameter.
2) The grippy surface is very small on them and located on the outer part - not very ergonomic, plus, depending on the gloves you'll be wearing, they're going to be slippery.
Rain only adds to the problem.
3) Due to their aluminum nature (and small rubber/grip surface) vibration-wise they're are all over the place, this, in conjuction with (1) lead - again - to hand pain...
They sure are well-built and look good (i.e:"bling factor") BUT, they're just that, only looks and nothing more unfortunately.
If you plan only on riding in the city i suppose they're OK, for small/long trips though they're going to be torture...
Just my 2 cents.