Well, first of all, If you have 1/2 or better cover, you dont get attacks of opportunity against you. Its very clear on page 132 of the PHB. Not alot of room open to "DM Interpretation".
It is my understanding that 3.5 shield is only getting clarifications, not a total rewrite.
I believe (but I have not evidence to back this up) that the new shield will be rewritten to reflect the changes noted in the errata.
e.g. Shield gives +7 shield bonus from one direction, and +3 to reflex saves on spells originating from that direction. Additionally, Shield protects the caster from magic missles from the direction the shield covers.
Notice how the only real change is how cover has been removed from the description?
The version of the spell that gives a +4 Shield bonus to ac, a +3 reflex bonus, and immunity to magic missles is the Neverwinter Nights version of sheild (Actually its in the upcoming expansion). They are making it this way because NWN does not account for facing very well, and having the player specify the direction of the shield will confuse the average user.
While both versions are fairly well balanced (and both belong at level 1, IMHO) I believe the pen and paper version needs to have the version of shield with facing to create more interesting strategies in game. Players need to surround a wizard, rather than just walk up to him.
Let face it, the +7 AC bonus is nothing when you are dealing with a wizard who cant wear armor. stacked with mage armor and a modest dex of 14, thats only an AC of 23. Sounds high, but most fighting types can usually hit that AC with little difficulty around level 6 or so.