You almost have to; I'm not even sure the archmage tree has 80 points to spend.
My problem with wizards in the EP isn't a problem for me, but a problem in general. When I sat down to plan out my wizard's enhancements I jotted down every single enhancement from both trees I might want. When I was done, I had a grand total of 86 AP in the list. Cutting 6 AP was a breeze; I essentially ended up with everything I wanted.
The problem is this: I was never interested in other types of wizards, but now (from my perspective) other types of wizards no longer exist. No more "which elements should I choose?" variety, no more "should I be a lich or maybe specialize in a school or 3 and spam SLAs?" decision, no more decision of almost any kind. The only choice now is "should I use forms or be a WF?" Because every archmage can easily afford undead forms now.
So while the "one wizard to rule them all" is all well and good for a guy like me who only wants one wizard, we sure have lost a lot of build variety when it comes to wizard.
For comparison, my ranger, paladin, cleric and fighter all had well over 100 AP in the initial list of everything I might want. Most were over 120. Paring down those lists to 80 hurt (in a good way) and left me feeling like I could roll up a second version of the class that had a totally different flavor.