It's pretty good right out of the box.
You could buy it and go play the next day.
But if you really want to upgrade it, you might want to get a new regulator and a better board. (Even though the LEAP Tado is amazing)
Pretty fast (25 BPS)
3-Point adjustable trigger
None that I have encountered.
Ok, so I bought this marker after coming back from not playing for a while. I wanted a gun that would keep up with some of the newer released guns. And let me tell you, I am not disappointed in the least. From the moment I took it out of the box I was happy. And when I took this bad boy out for the first time, I went from happy to amazed. It definitely out-shot my previously owned Ion XE, and for the price of it, it isn't far behind a Dangerous Power G3 (or some other mid-grade marker). In the right hands, this gun can lay down paint like a mo-fo.
Anyone who wants an amazing gun and does not want to spend a whole lot of money on a marker, I highly recommend this. Great buy for recreational players.
It is fast, light,accurate, and sexy.
You won't be disappointed.
Unless, however, you manage to find some way to break it. Even then, Kingmans tech group is pretty efficient.