I have used the spyder shutter which i believe is very much like this marker except for the fact that it is not as good the Enigma has much better accuracy, speed, and is just an all around better marker.
I use my Enigma EXR with all stock parts, I also have a Spyder Shutter, and a Rebel LE of all these guns the Enigma is most definitly the best.
I don't think it needs any upgrades really badly it is a very well put together marker but if I had to say something I would say buy better grips.
Everything this is an awesome marker!
This marker is very awesome it blows away both my other ones and I have just played for a few months and I can stand up against all my friends easily who all have spyder flashes and other electric guns. It is a very easy to field strip gun. I got the silver and asked my friends if it gives away my postion in the field and they said no and even if it does it doesn't matter because I win alot of the time anyway.
If you want a gun that is very cheap and good buy this gun! It is a 10 out of 10 for any class of gun.