Well, from the top. For this price of this gun, you cant go wrong in buying it. The expansion chamber, 12" barrel, vertical feed, rear cocking bolt, and simple stripable feild parts make this gun a good choice. Also the intruder has a compatability with the spyder markers, so what you can upgrade on a spyder, is surely to work for the intruder.
Well, nothing is really bad with this marker. Mine however had many leaks, but everyone I know that owns one has no problems. Also, if you have the extra 50-100 canadian dollars, you should consider the other markers which are slightly better, such as the Spyder 2000, Tl Plus, and the PMI Piranah.
In conclusion, this is a excellent marker for the price. And is compatable with spyders. I would suggest you look in to this gun if you're fed up with your low grade spyders or model 98's and want to spend some extra bucks for a quality marker, in this case about $25-$75.