Ok, the following is just my opinion, and only my opinion.
I test drove a 4.8 yesterday afternoon, while I was getting my oil change. Is it me, or is the 4.8 not as fast as I thought it to be? It feels like I'm driving my X5. I have an 01 4.4i sport. I swear it accelerates like mine, when I floored it, it hesitated like no other, it didn't feel any faster then my X. I understand what the stats are on the this type of car, but guy's I'm sorry, I didn't like it one bit

. The only thing that I liked was that the steering was a lot easier to turn. That's it. Maybe I was waiting for a rocket lunch or something. I drove a 4.4i 2006, 4.8is 2004 and a 4.6is 2002. The winner by far is the 4.6is. This thing is a rocket. So much more punch then the 4.8is. Maybe the whole tranny thing gives it the slight hesitation, but come on! I would like others to try each of these cars and post there opinions as soon as possible. I was even thinking of trading mine in for a 4.8is. Forget that. I'm keeping mine and just upgrading to the 4.6 body kit. Just thought I would share my thoughts. Thanks..