Just played through the demo and thought it was quite amusing. It's definitely true to the original with loads of newer stuff added into it, like writing on whiteboards, throwing faeces around like a tennis ball and interacting with tonnes of other stuff which is usually left out of most games now.
Demo is split into two parts, first being the stadium where you mess around for a while and then go and fight the cycloid enemy with the devastator weapon, then when you've finished that, you move onto one of the highway sequences in the duke truck. That level is most of a proper one and gives you a real idea of the gameplay. My one and only major annoyance with this is you can only carry 2 weapons at a time, compared to the old game where you could have as many as you wanted lol. Theres a lot of variation in the weapons on the levels, with the pistol being the M1911, stakeout shotgun and then the more exotic stuff like the nailgun, shrinkray, railgun and rocket launcher to name a few.
The pipebombs and tripmines are separate from the 2 weapon system, and you press 3 to throw a tripmine and 4 for a pipebomb, which makes it easy enough to do in the heat of battle.
From a graphics standpoint, it does look kinda dated in a few areas, mostly due to the engine its used, but the graphics options do support two different types of AA on my nvidia card (FSAA and FXAA) and you can customise a few options like texture and shadow quality etc, although not in the way most PC users like to see (ie you can't choose 4/8x AA as the game just decides for you, just the type of AA used).