Hopeing to add to this discussion, although maybe a bit dead now...
PES (including the new PES5) for PC is indeed not analog. It has been stated in the thread already, but there are only 8 directions available, whether using the d-pad or an analog stick. Thus, there are only 8 directions to strike manual passes in, and only 8 directions to strike crosses in.
I recently played the FIFA '06 PC Demo, and was pleasantly surprised to find analog support there. You see, I always thought that the reason PES didn't have analog support was that the dribbling system might be a big harder since you, right now, make certain dribbles (like 180 turn and sidesteping) by moving the stick 180 degrees, and pressing L2 and moving the stick/pad 90 degrees in relation to the way you are moving, respectively. Making things analog might make the dribbling less intuitive and more prone to errors and misjudgments.
However, FIFA '06 had a great solution. Basically, when you are in possession of the ball, the dribbling system is 8-way like in PES, making dribbling very easy. Crosses are still very analog and respond exactly to the way the stick is tilted. Off the ball, however, the movements are completely analog. You can run in every which way you want. Very nice.
In PES, however, off the ball you often have to fall back to wobbling the stick to run analog-ly. In other words, rapidly switching from running straight up and running to the up-right direction will result in the player ending up somehwere in the middle of up and up-right (making the player look slightly drunk if done correctly(or incorrectly)).
In my opinion, the only thing really missing from PES (everything can be improved ofcourse, even something so close to perfection as PES) is analog support. There are just to many occassions (in the PES5 PC Demo, but also on PES4 Xbox) where I have had the opportunity to make a player free with thew goalie with a simple cross, only to have it go too close to the keeper or to far away from the player "thanks" to the 8-way nature.
So, Analog support to me is a must to make those precise passes possible. I would use analog passing more (at all) if it was analog, since it would then work as a complement to ordinary passing and through-balls. These days almost all controllers are analog, so I don't see the reason why not to include it. I mean, even ISS '98 for N64 was analog in every sense of the word. And I never had any problems with dribbling either.
Well, those are my thoughts. Leave yours if you want. Meanwhile, I am off playing the PES5 Demo.