Ive never had the EXUP valve working since I've had my Fazer, about 3 years now. I don't know any different and I love it. Sure its a bit wooly low down but as long as you don't expect huge grunt below 3K its ok. The 7K speedo warning get a bit irritating, but ive learned to live with it. Wheelies are very easy off the throttle, just wind it on and up she comes, but thats because the power comes in steeper due to the having less power at the bottom end. So don't be frightened of just sticking a bolt through the EXUP plate and re fitting the exhaust if you want to ride it while you get the EXUP bits together.
Saying all that, i'm waiting for my new cables to arrive and I will be fitting my bike with the (mostly new) EXUP valve assembly, I just hope I can tell the difference once its done. Hopefully they will arrive before the weekend and I can report back on my thoughts before Monday.