It's not quite the same as using a GunCon, but a stylus will do the job just fine.
Many of the shooting games that were in the arcade versions of Point Blank are transferred to the DS wonderfully. An angry crowd throwing objects at Dan and Don performing on stage. Floating targets in space that spin from red to blue and back to red again. Skeletons. All the stuff that made the series cool in the 'cades is in the DS version.
There are also shooting games that I don't remember seeing in the arcades. Shoot the analog clock that matches the displayed digital time. Shear three sheep by shooting off their wool. All of the new things fall in line with the old stuff, all of which is off the wall and totally fun to play.
Of course, the original games used a light gun. The DS version replaces that with the touch screen and stylus. With just a few tweaks in some shooting games (like more moving targets), it still takes skill to shoot everything perfectly and correctly the first time. You can still miss things if you're off by just a pixel or so, and there's always the possibility of mistakenly shooting a bomb or the wrong color target.
For the most part, the game plays exactly the same as its arcade originals. I think this shows how well the Point Blank games were designed in the first place, and it looks like it's going to work just as well on the Nintendo DS.