As part of 4E, I did love essentials too. [I feel for those it burned, though, you have my empathy]
Essentials was a weird thing, but I really liked it. Fortunately, no one I played with got tripped up by it. I like alot of things about it, some that didn't even directly relate to D&D.
To list a few:
1) The books were small enough to fit in a small carrying bag or box, if you only had 1 or 2, they'd fit anywhere.
-This really should be a consideration for all 'Rule Compendiums' ever.
-Also, I think they were less intimidating to some new comers.
2) spreading out what characters get over all levels is fun.
-though this did prove a liability, i think, [see my rant at the end of this post.]
3) The classes were mostly pretty cool,
-quite frankly the slayer is the best thing for someone who doesn't know what they are doing (put them in battle fury stance and set them loose, occasionally have the DM prompt them to use power strike) AND still a lot of fun if you know what you're doing and want to play around with adding complexity to a simple class: I had a pike wielding goblin that was very tactical to play and used powers that didn't make much sense the first time i read them.]
-Its fun to play PHB1 version of the classes and have a feeling of 'retro' within the game. Playing an archery range from PHB1 feels to me like I took a 2e ranger into a 3.5 game, but everything still works...
4) they blended in with old stuff no problem. [at least, that was my experience.]
5) The _base_ rules (class neutral stuff: action economy, movement, healing, etc) didn't actually change, so I didn't have to re-learn how to play, BUT the approach to classes did so i got to re-learn how classes worked.
-It really started me down the path of mutating/improvising the system (specifically as a DM, as a player there are limits) After seeing what they did with the classes, I applied similar logic to how I approached creation of most other things in the game.
The downside I ran into: They made the essentials style classes a royal pain to make/develop.
In order to make a warpriest domain you had to make a batch of all new, unique, never before seen powers and features: 2 at-wills, features at levels 1,5,10, a utility, a channel divinity, encounter powers at 1,3,7,13,17,23,27, plus paragon path stuff (can't remember which bits), and usually some related dailies...
It was pretty bad. Even to make a 'simple' Slayer type meant having to craft things to get at the levels you'd usually get dailies, etc, and you end up with ~20 little things you have to come up with and balance. Should have been less specific, more options. I think that is why we saw so few domains, spell schools, virtues, pacts, etc. It was a hassle to build them. Shame that. I don't need one new 'domain' to come with 20 new powers, but I would like 10 new domains with maybe 3 new features and 3 new powers (with perhaps some sharing)?
But I still love essentials. They had a very big, very positive, impact on how I play the game.