Have to disagree with MiracleofSound and Woodsey. While the demo is rather short (got it 4 hours ago and already finished it twice on medium and once on hard difficulty modes) to make a proper opinion and, by the looks of it, running an outdated version of the game (development-wise), here's what I can say as a counterargument to some of their negative statements:
Before I write my statements down let me give a short description about the demo to the people who haven't had the opportunity to play it: This is a 30-minute long gameplay demo split into two missions: one that takes place at a football stadium (see DNF gameplay trailer from when it was first announced) -and- (I take a rough guess) the Nevada desert, where Duke runs around a little in a monster truck and then shoots his way through aliens to get to a mine.
First of all, excluding the blur, I didn't find the graphics of the game to look that bad. Honestly, I don't understand why people are so upset by this. Sure, it looks nothing like Crysis 2, but it's pretty damn good as far as I can see. Then again, I tried it out on a PC, so this might be console folks talking console stuff.
Second, whether you find the jokes in the game funny or not is purely subjective based on each person's humor. I found the jokes pretty funny. Unfortunately, after the first 2 minutes of gameplay, the demo cuts short on jokes, usually just sticking to Duke's one liners as opposed to the EDF soldiers funny lines. Still funny, but not as good as what you're presented at the beginning.
Third, combat. I didn't find it that bad, really! The first part of the demo was pretty short on that, and That is kind of a bummer (it's pretty sad when a 30-minute demo has about 5 minutes of running around in a -shooter- game), with the only combat segment of it being the boss fight, but I really didn't find it -that- bad! Sure, it could use a little tweaking to make it more intense but, as it is, it's still a pretty cool fight. Woodsey was incorrect in his statement in which he said "standing around". You have to move constantly during the fight in order to dodge rockets, a charge that the boss does and a ground slam which goes in a straight line. The rockets alone take about one third of HP on medium level and half HP on hard, so it's essential that you don't remain stationary. This, combined with the fact that a friendly chopper drops ammo supplies whenever you need them, BUT, in random locations makes it a pretty interesting boss fight.
The combat didn't seem as much "cover shooter" to me as it did "keep moving at all times", a la Serious Sam. Taking cover is only a good idea when you need to reload or when your health drops drastically, otherwise enemies will draw in on you and you'll get wasted so it's recommended to stay in the open and constantly move to avoid enemy gunfire, while shooting them down.
Fourth, not everything is brown. The first part of the demo, at the stadium, has a rather wide arrange of colors from what I was able to notice. The second part has, indeed, brown as the predominant color, but honestly, it's a desert setting, what would you expect? Besides, from all the released trailes I think the game will be anything -but- brown.
(Let me make a short pause here to discuss the health system. Yes, health kits are missing and the health regeneration system is implemented, but I don't see it as a bad point, seeing as the game is rather challenging on higher difficulties. For me, this seemed like the kind of game where standing still meant that enemies would instatarget you and hit you, but moving meant you had a chance to dodge the bullets. In this kind of scenario, having regenerating life almost seems like a plus, since you can't rely on cover to actively fight your enemies, just to reload and recharge health.)
As for framerate issues during gameplay, I played the demo with everything on max and I had no technical issues with it. The rig I'm currently using was set up in 2008, so it's quite old, but not outdated, and it does run all the CoDs, Crysis 2 and Battlefield BC 2 on it on mostly max settings (the only game I had to put at medium settings so far was Battlefield BC2).
Please don't get me wrong, the demo DOES have flaws.
The driving section is rather tedious.
The blur seems to produce minor graphical issues witch can diminish game quality and make it feel like a cheap remake.
The fact that you can carry just 2 weapons is simply bullshit. I would've accepted 2 weapons + a gun, honestly, but it feels retarded when Duke has to throw his gold-plated pistol to pick up a shotgun. Honestly, you can't just squeeze it in your jeans or put it in a holster on your leg or something?
The fact that it is clearly an outdated version of the game and still presents minor gameplay issues. It just feels like they took a last-minute decision to release a demo and de Devs and QA departments found themselves with 2 days to create something shippable.
Hopefully, most of these issues will be already resolved in the launch version or in the first patch of the game, and some (like the weapon system issue) in a future DLC or larger patch, but my best advice to you is:
Just look for the demo gameplay on Youtube. You shouldn't decide your choice on other people's opinions since opinions can be subjective, especially when talking about games. If that doesn't convince you, wait for the game launch, when the demo will most likely go public.
I agree with everyone else that Gearbox and/or 2K Games did a dick-move by giving the demo only to FAC members (though I can understand the motives, it's really an ugly way to crap over a big majority of your fan base).