I think it really depends on your suspension curve. Either extra volume can does make the shock progress through the travel easier, and that will have a potentially unwanted effect on a naturally linear and certainly an unwanted effect on a regressive linkage.
You will feel like you lose some mid/low end support, but sometimes that suits people.
Saying that, there's nothing like the feeling of a custom tuned shock!
Just to clarify, I tried it on a Float X with a Yeti SB66c, and a friend had it on a Specialized Camber.
The Yeti and the extra large negative spring didn't mesh, the addition of air beyond 210PSI had no effect on the sag point, which was sitting around the 30% mark, far too low for the switch link to work properly for the way the bike pedalled. Extra pressure affected the bottom out point alone, I inflated up to 300PSI at one point just to see if it would change, but could not achieve less than 30% sag thanks to the breakaway of the massive negative spring, it would still leave travel in reserve, but it would "bottom" harshly even if it didn't use all the stroke.
The Camber, probably more understandable, Specialized run high leverage rates on their frames, so the same issue with it blowing through travel. However the same issue wasn't noted with the EVOL upgrade after the shock was serviced, hence the recommendation.
Might help add some context to my comments.
