I have a full metal version and with the tightbore and red dot it is great. I use a battery sling as it saves faffing around with the peq or removing the front end to put a battery in it.
As with all ICS the gearbox is chainsaw and you cannot help but grin when you fire it. Range is very good, as good as my AK. With the tightbore the accuracy is quite good as well. They do need downgrading from new as most fire around 380-400fps. I have mine at 325-330 so I can use it wherever I play. Split gearbox makes spring changes and piston changes easy.
It works with ICS mags very well and ACM mags quite well.
As for aftermarket external parts, well it has a rail system, which is standard so you can happily put loads of crap on it. You can also change the stock easily if you want. Apart from that you buy it for its looks out the box, you want something customizable, then buy a standard m4.
For something that does not look like anything else, its a great gun, that performs very well and will give you a grin when you fire it.