The GS (or TP now I guess they are with the X-chamber, V-bolt and Zero-G barrel) is great out of the box, and doesn't really need any upgrading. I got a drop-forward, just because it felt a little back heavy with the 20oz tank, but that's a matter of personal preference. I'd also recommend the Ricochet, even though I've never had a chop in about 5 cases, I have had feed problems which robbed me of a few easy eliminations.
Great package out of the box...but ONLY if well lubed, otherwise, you will bust seals. Velocity consistency is great once properly adjusted, although I had to clip the spring to get the thing under 350 fps the first day I played with it. Other than that, it's stayed fairly consistent +/- 5fps. Very easy to completely strip and clean.
The trigger pull is a little heavy and difficult to rip off long strings of paint, but it's just fine for snap shooting and short bursts. Also, the enclosed cocking system is great, BUT.....I took a hit to the powerfeed tube and it was extremely difficult to get the inside of the quick-slide rail cleaned out after that. I'd recommend making a small wooden block to go in the front and caulking it in with some clear silicon caulk (so that if you should ever need to...shudder...remove the sight rail, you can use and x-acto knife to remove your plug). Bad idea to remove the sight rail, as it's very difficult to re-attach without stripping out the screws. Remember they're steel into an aluminum body, so you'll strip the reciever before the screws. The same thing goes with the trigger frame, be careful and you'll be fine.
Great package....the best you can get for under $300 (that's the whole package, not just the marker), ballistics wise, it shoots just as well as the average autococker or other mid range ($400-700) marker without expensive upgrages. Obviously it's not an Angel, but it IS the best of the blowbacks, and competitive with many more expenive guns. Sure, you can't shoot long strings of paint, but that's just wasteful anyway......this is a semi-marker that is quite accurate, yet allows players to develop their skills rather than just hide behind ROF. For what it's worth though, I've had some friends with VERY fast trigger fingers, and they couldn't get my F4 to chop paint, no matter how fast they shot.