I have owned and used my Tippmann Sl-68 II since 1996. During that time my marker has seen very heavy use by me and others. As a former paintball field operator, I often loaned my marker out to my regulars. There are many things that I like about the marker and a few things that I don't. This review will cover my experience with the marker in detail.
Accuracy: My marker has always been extremely accurate. Especially with the 16 inch All-American pro-lite barrel that I modified to fit the gun.
Locking Bolt: The bolt locks in place after the marker is cocked. This prevents double feeding and creates a stable platform to shoot from since the slide does not move.
Iron Sight: The SL-68II has iron sights, and they work. You really can hit what you aim for with this marker.
Autotrigger: The marker is equipped with an auto trigger. This allows you to hold down the trigger and simply pump the marker. The gun will fire each time the bolt goes to the forward position. This is extremely useful when you are in a tight situation and need additional firepower. Just be careful not to chop a ball when using the auto trigger though.Cleaning: The marker has an access port on the side of the gun. This allows you to run a squeegie through without removing the barrel.
Small Grip: I am 6ft 3inches tall and have large hands. The pistol grip is slightly too small for my hand. Its not a big deal really, and does not affect my ability to use the marker. However, I do notice it, especially as the day goes on.
Small Feedneck: The feedneck is smaller in diameter than modern markers. You must have an adapter to make loaders fit. The feedneck is also prone to cracking if it is over tightened.
Lack of upgrades: You can't really upgrade the marker and after market barrels are hard to find. You can find them, its just not easy. That's why I had to modify one to fit.
Lack of Ball Detent: The marker does not have a ball detent. This allows smaller diameter paintballs to roll out the barrel if you have it pointed down.
My marker is extremely accurate with the 16 inch Smart Parts All-American barrel that I modified to fit the gun. Head shots are no problem even at extended range. I have played with, and owned many guns of all levels since I began playing in 1986. The SL-68II is my favorite, bar none.Additional Info 4/2/2011: I have been back to the field with my Sl-68 II several times since I originally wrote this review sometime ago. As stated previously, I bought my marker new in 1996, making the marker 15 years old. I finally had my first issue with the marker several months back when the o-ring on the rear knob failed, causing a leak during a game. A quick walk to the pro-shop to get an o-ring and I was back in the game. That O-ring is the only thing that I have ever had to replace on the marker.
Update 6/10/2013....gun still performs like a champ