I have no problem either way. In fact I don't really see what the differences are (in terms of monsters). The stat-block layout in Pathfinder is slightly superior, but I'm happy with the 3.5 style.
The differences are subtle to a casual glance, and those unfamiliar with the new system, but in play they actually lead to some pretty significant changes.
For example, Elementals are now Outsiders- no such thing as an Elemental type anymore (instead it's now a subtype of Outsider).
Undead have a smaller hit die and are no longer immune to critical hits or Sneak Attack. Also, Undead with mental ability scores are no longer totally immune to damage to those scores (IIRC), though they are still immune to drain. They are likewise not immune to mental effects the way they used to be, though of course individual templates can still provide immunity.
The "Grapple" modifier no longer works as it did in 3.X; instead one now uses the unified "Combat Maneuver Bonus" for
all special combat maneuvers such as Grappling, Overrun, Sunder, and Disarm. To that end, every critter and character now has a "Combat Maneuver Defense" which works against CMB just as AC works against standard Attack Bonus.
Finally, many skills have been merged together (such as Forgery and Speak Language into Linguistics, Hide and Move Silently into Stealth, Spot and Listen into Perception), which greatly reduces the number of rolls one makes in typical play (albeit making some skills "super skills" because they're so much more valuable than others- Perception being the obvious example). Also, the old "x4 skill points for 1st HD" is gone, and cross-class skill ranks are no longer halved (class skills now just grant a +3 bonus), so it's much easier to set up skills for NPCs and smart monsters.
But as you can see, a lot of stuff you put into Ascension is rendered obsolete in Pathfinder. So it'd take some work to adapt.