I like the concept, although I think the nacelle needs a little work. The blue ribbon warp grill seems a little tacked on.
Another problem is that the Ex-Astris "Star Trek" Enterprise is far from accurate.
If you're a member of Scifi-Meshes.com, go here for TobaisRichter's Enterprise model.
http://www.scifi-meshes.com/forums/3d-wips/56513-uss-enterprise-star-trek-2009-a-34.html#post400426 The side view is much more accurate and detailed. However, that being the case, it may be a little harder to photoshop.
And now for my real critique of the design. :p
When designing an Enterprise refit, you've got to remember why it looks the way it does. The nacelles especially, the nacelle mounted bussards resemble, at least to me, a thinned out front grill of a 70's BMW. In my design, it looks like the air intake in front of the rear wheels of a mustang, another very 70's look. As for the warp grill, the long ribbon is canon, but does really fit with the new JJ look. The JJ design is more about keeping hull detail small. Maybe something more like the bottom of the nacelle in this frame from the new trailer:
http://img99.imageshack.us/img99/9904/startrektlr3720p3040.jpgAlso, something I tried to do with my design, try and keep the distance in height between the center line of the deflector and the center line of the nacelle, meaning if you move the deflector down, move the nacelle the same amount. Helps to keep the feel of the new ship.
One last suggestion. If the new Enterprise was a car, it be a 1957 Bel Air
http://www.universalautosalesandclassiccars.com/images/1957%20Bel%20Air/57BelAirLeftSide.JPGIf the refit were to be a car, it be a 78 Camaro
http://camaro-central.com/news/uploads/2008/06/78camaro2.jpgMight help, it helped me. :p