I haven't used the E1 illuminated, but have used the regular 2-7.
Bought one with a buddy who had never set up a scope before, so I helped him and then we hit the range. First thing that I wasn't big on is the fact that the magnification adjusting ring is larger than the front bell, which caused mounting problems on his remington 700 long action. The adjuster was touching the rifle with burris medium rings. That's not a huge deal, but it is frustrating that you can't mount the scope as low as you can mount other 2-7's with the same size bells.
The other thing I wasn't wild about was the parallax problem with the scope. If you sight something the crosshairs move on the target if you move your eye. In other words, you must have a very consistent cheek weld to be repeatable with that scope. I have since checked out the redfield in 2-7 and it has no such issue. Plus the magnification adjuster is smaller diameter than the front bell (allowing you to mount it lower), the glass is better and the warranty is easier to claim as it's through leupold, not burris.
Edit to add, I have a fullfield 2 (predecessor to the E1 with a more traditional reticle) 2-7 (non illuminated) and it has none of the above problems. Sorry, no exp. with the illuminated model.