I've had mine for about a year now. When I purchased it, it had already been used for a few months by two other people, and the only things it has needed in all that time are a new spring kit, a couple tune-ups, and regular cleaning (just as with any firearm).
The hop-up is a bit inconvenient to adjust, as it requires removing the slide, but that's really not a problem since you shouldn't need to adjust the hop-up during a game anyway. Be very careful to not over tighten when adjusting, because the plastic threads can strip fairly easily. This is what happened to mine, and although I have to take apart the barrel assembly whenever I want to adjust the hop, it forced me to discover an easy mod. Since hop-up mechanism no longer stays in place, due to the stripped screw hole, I have to lock it in place by wedging a rolled up piece of tape between the hop-up lever and the outer barrel. Doing so eliminates the possibility of the hop-up mechanism moving during use and affecting the BB grouping consistency. I measured off the range this summer (performance is always best in warm weather), and at 155 feet I was getting groupings with a 3 foot diameter on average, and most of the inconsistency was due to my aiming, as I was shooting from an upright position.
Very solid construction. Although it is not recommended I use Crosman CO2 cartridges, not propane or green gas, and I have never had any problems with any parts failing. I avoid using gas guns in the winter months, as they do not preform very efficiently in cold weather. During warm months, I can run 60 to 95 rounds on just a single canister. In the cold months, only 20 to 30 rounds.
Very light weight and reliable. Sometimes I drop my CQC M4 and take only this into the field. The times I get the most kills are usually the times when I use only my M9 and my rubber knife (those are always the most glorious kills as well).
I recommend cleaning and re-greasing after every event. Because the slide is open, it is more likely to accumulate dust and debris if you are not careful. But don't worry; disassembly is very easy. There are also an abundance of aftermarket replacement and upgrade parts for this gun, though I don't see any reason to upgrade until something breaks, which I predict will not happen for a long time yet.
Simple design. Simple to operate. Similar to a real firearm.
High availability of aftermarket replacement/upgrade parts.
Abundance of disassembly/reassembly videos on youtube.
Very reasonable price. You don't need a $150 KWA.
Very comfortable, especially if you purchase the ergonomic grip for it.
Very natural shape. Easy to quickly line up the sights.
FUN to use!
Open slide can accumulate grime.
Hop-up unit can strip (was s good thing for me).
Safety mechanism is hard to disassemble.
Hard to find replacements for a couple of the smaller springs.
Rating: [5 of 5 Stars!]