In a nutshell, brilliant fairy-tale story (Planescape Torment's story is the only game that comes close). Just sit back and take in two of the best adventure games the PC has to offer (to date Feb 2008!). Once you are finished with both, you WILL want another sequel and the various plots will have you thinking about the games even after completion.
First off, the contents. The limited edition comes with the original DVD (equivalent to the 2-CD version) of The Longest Journey (TLJ), the sequel on DVD, the 22-track CD soundtrack to Dreamfall and a hardback book containing concept drawings (some in colour) of Dreamfall. So if you haven't played any of the two games, the limited edition is a must! On my old AthlonXP2000/1.5Gb RAM with GeForce 7600GS and X-Fi, both ran flawlessly.
The graphics for TLJ aren't the best these days but trust me, that won't matter. Dreamfall, on higher settings at least, looks the bees knees of 2006. The voice acting is very, very convincing and the music is undoubtedly worth listening to outside the games. However, the story is the selling point. TLJ is the better of the two and deeper (by a bit; I'm even saying this, cutting a long story short, having played the sequel Dreamfall before TLJ - take-home-message: play TLJ first). The plot is very apt for those in their early 20s, at college/university. I say this because you will almost certainly empathise with the key characters, April and Zoe. The story is often sad at times, especially near each respective finale but also hilarious (the Crow!). There will be plot holes that need filling but that's where the sequel to Dreamfall should come in.
Gameplay is different for both. TLJ is click-and-she'll-move type affair, usually with the camera static, often viewing from quite a distance. Dreamfall is more Tomb Raider style i.e. more up-close moveable camera, sometimes annoying when in combat. Both games feature interesting puzzle elements. TLJ has no combat (April can't die by your hand) and the game lasts longer than Dreamfall. The combat in Dreamfall is reasonably easy. Some authors commented that the combat should have been omitted in Dreamfall, which is understandable. For me, Dreamfall was so heavily focused on story that the combat sequences provided a respite and did not detract from the plot.
By playing Dreamfall after TLJ, you will notice the welcome return of some of the original characters (and their voice actors) and locales. All of the characters you meet in these games are highly memorable and the story is balanced with enough detail without feeling overwhelming. The only downside is that in TLJ, you need Dreamfall in order to fill the plot holes. Dreamfall is a bit short and the combat takes getting used to. However, this edition gets 5 stars because it comes with both games. With the myriad of PC games focused on graphics and all out action, it is reassuring that games like Dreamfall are conceivable. The fact that I also thoroughly enjoyed TLJ supplied in this edition is a testament to its success, given that TLJ is over 7 years old!