The thing that baffles me most about Dungeons and Dragons Essentials is the question of "why?" What purpose does this line have in the grand scheme of Dungeons and Dragons, 4th edition? Why did they feel the need to "reboot" the edition, several years in, as opposed to reprinting the core books with errata and rule changes included?
Heroes of the Fallen Lands is the first book in the Essentials line of products besides the Starter Set, and is intended to guide players through the creation of low-level characters, as well as more broadly introduce new players to the world of Roleplaying Games generally. It begins with a very verbose section of what a RPG is, what you need to play it, how you play it, and general questions that were already addressed, in an abbreviated fashion, in the Essentials Red Box, and are very similar to the introductory words of the Players' Handbook. Heroes of the Fallen Lands does explain some of the basic mechanics better, and much earlier in the book, so it seems that their editors are not sleeping.
We are introduced to Dwarves, Eladrin, Elves, Halflings, and Humans in HotFL, and we are also told that in the followup volume we will also be introduced to Dragonborn, Drow, Half-Elf, Half-Orc, and Tiefling characters. Then, most maddeningly, we are also told that there is another type of character, a Revenant, which is only available if you pay for a subscription to Dungeons and Dragons Insider, the nebulous online service that is not sold very well in the description. We are also told that HotFL will tell us how to develop a Knight, a Slayer, a Warpriest, a Thief, and a Mage character, but for others (Sentinel, Cavalier, Hunter, Scout, and Hexblade), we have to buy the other book. And again, if we want to learn how to make an Executioner type character, we have to pay for a subscription. Then what follows is a very reasonable and straightforward step-by-step method of creating a character, something that the Players' Handbook completely and utterly lacked. Largely a lot of information that the PHB waited for the closing chapters to introduce is up front and center in HotFL, and much better organized.
In the "advanced" sections explaining what each character class is like and what it does, it spends much more time than the PHB explaining why some races are better at certain classes than others, as well as gives personalized level tracks for what each class gets at what level; as this is very streamlined and there is a dearth of options, leveling is a purely mechanical affair that minimizes player decisions and resembles more leveling up in Final Fantasy. While it walks each character build from level 1 to level 30, it is a purely linear progression. There are very few variant builds for each broad class (Fighter, Cleric, Wizard, etc). We are occasionally told that we could build a variant character if we had another of the books, but it seems pointless to add in little asides like that, as they do nothing but advertise for your own product.
There are slight differences in the races section, as pointed out in a previous post, but nothing radical or crazy. Like I mentioned before, I don't see these as variant rules, as these alternate builds would work perfectly well with PHB-built party. Hey, even the art is the same as in the PHB. It's mostly just copypasta, with a little bit of extra stuff added in that doesn't really have much of an overall effect on how D&D4 handles races.
In the skill section, we see that DCs for different levels of challenges have been fiddled with (made easier), but other than that, more copypasta. Perhaps the skill applications are explained a little bit better than in the PHB, with little examples peppered in for how each skill might be utilized in an encounter or a social situation. Feats have been (strangely) categorized into what "realm" the feats fall under, so there is a group of feats dedicated to learning and lore, another dedicated to endurance and stamina, another to weapon and armor proficiencies. So rather than just long lists as in the PHB, they are subdivided based on what the feat does for you. The book ends with armor, weapons, magic items, and the like, that are largely lifted directly from the Players' Handbook.
What the Players' Handbook has that this book does not are lots of pictures of what Burst, Blast, Wall, and so on actually look like in terms of squares. But that chapter from the PHB is available online from Wizards.com as the "Quick Start Rules" so that is not a big deal. All in all, there is not enough changed to really justify buying this if you already have a copy of the PHB; if you get the Deluxe Dungeon Master's Screen it has all the updated DCs and damage levels, and so ignoring all the Wizards Weirdness about DDI and temporarily forgetting that that exists, there is no reason to get HotFL if you've already got the "other" player handbook. It's much less information, in a smaller book, at a lower price; but which is also better organized, better explained, and easier to follow.
Overall I'd describe this book, and perhaps by extension Essentials, as being a form of "pregenerated characters plus." Following the steps makes a very generic character, much like starting with a pregen, but there are a few small flourishes that the player can add. With the linear level progression, it is again very pregenerated feeling, and a player can choose to follow the track for that character all the way to level 30 or, as I suspect the intention is, act as "training wheels" as long as the new player needs before they are interested in buying OTHER Dungeons and Dragons products, like the Players' Handbooks or the * Power books. For this reason again I don't think that Essentials constitutes any reasonable step towards a "4.5" edition, but is rather a hyper-simplified form of the "real" rules and is intended exclusively for beginner players without any reasonable RPG experience. It "essentially" (ha ha) walks players through the learning process (something that under the core rules is assumed to be under the purview of the DM), taking some work off of the DM's side, and I don't think that's a bad thing.
Is it something that somebody who has already been playing D&D4/has already invested in the 4e core books would want? No.