I received my new rifle today, by way of Speed post and USPS.
I was in the middle of cleaning up my kitchen when the postman came by, and when I heard him ring the doorbell, my heart almost stopped. I hastily signed for the package, almost too excited to write my own name out. Although it came in an inconspicuous brown box, I knew instantly what it was.
My anticipation almost overtook me to open it up, but alas, I had to first clean the kitchen as I was leaving for work in 30 minutes. With my chores complete, I rushed over to the kitchen table with my handy box cutter. I literally ripped through the outer packaging to get to my new gun. WarGameClub was kind enough to turn the gun's box inside out to avoid any trouble with customs, but alas, there was a note on it. The United States customs service provided me with a copy of the regulations about marking the barrels of replica firearms.
With the tape on the back of the box cut, I lifted the lid to my new baby.
[Pictures, unopened box, then contents of box]

And boy, is she a beauty. All a nice, non-reflective black, except for the chamber, which is fine with me. I spent so much time ogling over the rifle that I almost forgot there was other stuff in the package. There was Marui's little package with their catalog, targets, and safety rules; as well as the suppressor, a bag of BB's (not sure what weight), the barrel rod, and the upgrades I ordered.

Specifications:
Rifle:
Length: 37.5"
Width: 2.75" at widest, 1.5" as thinnest
Height: 6.5" from bottom of stock to top of mount
Weight: 4 lbs, 5.35 oz.
Magazine:
Length: 4.5"
Width: .875 "
Height: 1.5"
Weight: 1.4 oz
Suppressor:
Length: 7.25"
Diameter: ~1.875
Circumference: 4"
Weight: 3.3 oz
Bolt Pull: 3.75"

Looks/Feel
The rifle looks absolutely stunning. The stock has a nice smooth finish with almost no bumps, and the seam lines are almost invisible. I believe that the stock is just plastic, though I cannot be sure. ADDED: It appears that the stock is not hollow on the G-spec, as there is no hollow sound emitted when the stock is tapped.
The rifle feels very solid, though front heavy with the suppressor installed. The chamber/bolt is a polished metal, most likely monkey metal, but looks very nice. The bolt handle is metal, very sturdy, black (slightly glossy), and comfortable.

On the left side of the rifle are the Tokyo Marui warning sticker, hop-up adjustment bar, "Warning: Refer to instruction manual" and "Tokyo Marui Made in Japan" engravings, as well as a serial number. Oh, and ASGK as well. There is no writing on the right side of the rifle.

The suppressor has the words "G-SPEC SOUND SUPPRESSOR" as well as a serial number and the TM label in white ink on it. The outer shell of the suppressor is metal, because it was squeaking and grinding as I took it apart to look at the baffle system. There are individual foam rings, followed by a slanted plastic ring, which I believe is to keep the foam in place.

The magazine has only the Tokyo Marui label on it, and is made of plastic.

Performance
As of this moment, I am unable to get accurate measurements, as it is 12:13 AM. What shooting I did get off made the rifle prove itself right away. With hop-up at the lowest point on the bar, I was hitting a soda can at 40 feet every time, even when it was rolling off my deck. With a little bit of tweaking on the hop-up, the included BB's were traveling across my yard, and my neighbors yard, before disappearing.

I will be getting accuracy and power ratings sometime tomorrow, though not in the morning, as I will be sleeping in.

The Suppressor:
The included suppressor is very nice indeed. Its foam baffle system changes the muzzle tone from a sharp crack to a dull whoosh, which is infinitely quieter than the original. I expect with all the background noise at a game, this rifle will be almost silent.

Overall Feelings
I absolutely love my new rifle. From it's solid feel to wonderful stock performance, it absolutely floored me. I expect, with the upgrades I will be installing (and comparing), I will be virtually untouchable in a game (if you saw the people I play with, you would agree). I highly recommend this rifle to anyone looking for a good stock performer. I also recommend WarGameClub, for their great prices and fast shipping (Got to my door in 5 days).

Accuracy Tests
Original accuracy tests were nothing to be excited about, though not horrible, they were not up to my expectations.
30 Ft, 10 Rounds, Supported sitting.

Notice, on the non-hop up target, there are only 9 holes. I did not miss, as I heard the thwack of the BB on paper every time. That means that 1 BB went through the same hole as another.

With hop-up, the groupings got a little worse, which is to be expected
(see picture below)

Second accuracy tests yielded much better results, with ¾” groupings at same distance, with Infinity .28g BB's
.2g BB's yielded even less promising results, with approximately 1” groupings at the same distance

Upgrading
Upgrading this gun is not the hardest thing to do, but not the easiest either. It requires basic use of power tools, as well as a good common sense.
To open the stock cylinder, you must drill out a stainless steel stopper pin, which requires either a drill press, which is highly recommended, or a very steady hand with a normal power drill. Make sure that you use a drill bit small enough so that you do not cut through the cylinder O-ring. It would require a drill bit much larger than the pin itself, but it is a point worth mentioning.
After the pin is removed, it is a simple matter of pulling the components out of their respective places, replacing them with the new pieces, and sliding it back together. When reassembling the cylinder, I would highly recommend using Teflon tape on the threads to insure a seal.
The barrel upgrades for this gun are just as simple as the cylinder upgrades, and without the drilling to boot. Simply remove the front screw of the scope mount (after taking the receiver out of the stock, of course), and unscrew the outer barrel. Take out the Phillips screws on the base near the mag well, and remove the hop up lever. Slide the assembly back out of the outer barrel.
Remove the screws on the side of the hop up unit, and carefully remove that side. Take a look at how the internals sit, as you’ll need to put it back together. Take the barrel out, slide the hop up off, and then replace the new barrel. Repeat above steps backwards.

Here are some pics that were taken of the rifle.