I missed the boat on the Deus Ex games when they first came out, but I picked up 1 and 2 on a Steam sale last year. I originally thought the first one was insanely difficult (at least before investing skill points into rifles, the bobbing thing made me seasick). I also didn't think the second was as bad as a lot of people did, but they definitely majorly dumbed it down for consoles. I recently re-played the original game to get myself geared up for DX:HR, and this time I made a point of investing my points wisely so I could boom-headshot MJ12 commandos from a mile away. I didn't finish replaying invisible war before HR came out, and now I'm actually starting to replay HR before going back to 2 (if I even do...last time I tried to replay SW:KOTOR I lost interest, but it was also my third or fourth playthrough). I guess my point is: I consider myself a fan of the series.
I really enjoyed the new game, I got it on steam preorder so I saved like 5 bucks, but I would've paid $50 or $60 or whathaveyou for it and still felt content. The only thing I'm pissed off about is that I didn't get the augmented edition so I couldn't have a silenced sniper rifle (it was my weapon of choice for the first two games). I don't mind them having DLC, and I'm looking forward to the upcoming DLC campaign (even if it's not free), but I really wish they provided an option for me to pay to get the 'augmented edition' extras, mainly that freakin' silenced sniper and 10k extra credits.
The good: It played very much like a modern day version of the original game(s), with some things streamlined, but in a good way that honors the roots of the first game, not the dumbed down aspects of Dx2.
Possible sort-of spoilers below (not story related, but felt like a warning was in order just in case)
Required boss fights are unfortunate, considering that the original allowed you to essentially be a pacifist, but if you have a certain augmentation that unleashes crazydeath in a 360 degree orientation, they're really not hard. True to DX form, I wasn't 100% happy with ANY of the endings, really. And by that I mean the in-game choices you can make at the very end of the game...there are video things at the end (instead of any in-game cutscene to speak of) which I found a little out of place and somewhat unsatisfying.
Other thoughts: I completed the game on the standard difficulty (not the hardest, not the easy one, the 'recommended' one) with extra praxis (augmentation) points left over that I hadn't even spent. I'm not saying it is an easy game, because I'm the kind of person who saves before pretty much any encounter, because I want to do it in the best way I can. That helped me gain the max benefit from situations most of the time. Also, I played at least a solid 22 hours, which imho isn't too shabby, when I'm still champing at the bit to play it again almost immediately.