The gun is small, but heavy, and well-made. The Anodizing is very durable. I chopped the barrel, put on a 45-round hopper, hooked it to a remote and made it into a great little sidearm for games where stealth is useful. There are three adjustment screws that determine whether it is frugal or wasteful with the CO2 (its more reliable when less efficient but rather bone-jarring to fire), and tuning it properly will reduce the noise a little. Field strips completely and quickly.
There are very few aftermarket parts. The barrel had very poor finishing (there is a visible groove in the barrel along its length). The valve is VERY fickle, and it frequently jams, especially in the cold, or when hot from the sun. Does NOT like liquid CO2 at all, and will cause it to jam. Has more kick than a Tippman (except a .68 Special), and is very loud. Hard trigger pull makes it a slow-firing gun, although this could be helped with a double trigger and some lighter-action springs.
If it wasn't for the poor valve design, this would be the perfect introductory marker. It (namely, the valve) is unreliable enough, that I have never gone a full day playing with it exclusively. I highly recommend a remote and an expansion chamber, this will keep liquid out. Since the valve is 90 degrees off from the hammer, the hammer places torque on the valve pin which is what causes it to jam. A frozen valve assures that this will happen frequently so KEEP IT WARM! The T-Cat is pretty cheap, but I wouldn't recommend it to anyone who doesn't want to keep adjusting their gun all day long. It works well for the specific role I have outlined for my personal use, which is why I keep it around, but it's internal operation is so fickle that I can't see using it in any extended situation like a scenario or tournament.