I like Geissele products in general, but I see this one as kinda pointless.
I prefer Damage Industries and Sprinco springs with a traditional sized buffer and less cost. Damage states their enhanced springs are good for 750,000 cycles. Sprinco's are supposed to be good for 1,500,000+. Damage is $6 on sale + shipping. Sprinco is $20 delivered.
I would be more receptive of Geissele's spring if it used a standard sized buffer and cost a little less. I just don't see paying extra for a spring that lasts 150,000 cycles and uses an odd buffer.
ETA: To be completely fair, a regular H buffer is about $30 and a Sprinco is $20, so it's only $15 extra for the G product. It's also sold as a pair and the spring will last as long as your rifle does, so its not like the funny sized buffer is really going to cause issues.