(IMHO)
It's all about fitting the tractor to your operation...
I have a 5093E that I bought new in 2009. I absolutely love the tractor. The first cab tractor and largest tractor we have ever had on the farm. For the price I paid, I think is/was a great buy. It's been a reliable and dependable tractor the whole time I've owned it. Never once have I had a need that my 5093E did not accomplish. I feed a 40 head herd all winter with it and I use it to cut/bale about 300 4x6 round bales in the summer. The tractor has been 100% for what I needed. If Deere did not offer the E series models, I would be unable to justify "paying up" to the M Series for my size operation. I probably would have gone with a lesser brand for lesser money. I'm very glad I did not have to make that choice. I got the dependability and support of my local John Deere dealer which is worth a lot for me.
Now, I'm sure their are JD owners that would look down the nose at the E series. Their operations demand "more" tractor than the E series offers and so they own either the M series or the R series. That is why Deere basically offers 3 different models around the size of mine. It would make NO sense for my needs to pay more than what I paid for my E series. There are other operators that would be very unhappy with an E series for their operations. That's not a reflection on the tractor, but rather a reflection on whether that tractor is right for their intended use.
I'm a believer that the E series is a great tractor if it fits your operation. For me, it's perfect... If it is right for your operation, I would highly recommend one.