I have a 1998 F4. The gun works great. It is easy to maintain, gas efficient, and easy to field strip. I got it from my wife for a wedding present, and have been playing with it ever since. It field strips without any tools, using only a screw on the bolt plug to pull the pin that connects the striker and the bolt. I like the fully enclosed body with the ambidextrous top cocking. It helps to keep dirt and stray paint from entering the internals of the marker. It is fairly lightweight. It also give you the ability to go with either the supplied bottomline, or to go with a vertical bottle. The all-weather valve is nice for playing when the temperature starts to drop.
It has a plastic trigger frame with a separate plastic "Euro" grip. It is rather uncomfortable, and know one seems to know where to get a replacement grip (I think a grip for the Spyder Compact will work, but...). The trigger pull is a little sloppy, but then again this is a low to mid level marker. The entire trigger frame and grip are different on the 1999 and later F4's. However, my most serious problem has been with velocity adjustments. The velocity adjuster doesn't seem to make a difference. Tried cutting the striker spring, but no good. It shoots at 300fps! Customer service at said it should settle down after about a case of paint. It didn't! Tried replacing the spring and several other things. Now I'm trying the aftermarket adjustable venturi bolt. If that doesn't work, I'll either get a regulator or ditch the gun. Other than the velocity trouble, it works great. The stock barrel is OK but could use upgrading.
Other than the velocity trouble, stock barrel, and the poor ergonomics of the grip, the gun works great out of the box. I got a CP barrel and that helps with accuracy and quietness. The 1999 and later versions get rid of the grip problem. I haven't heard of any velocity troubles with the 1999's either (maybe mine is an isolated incident?). You can get a new 1999 F4 for as little as $135. On the other hand, you can get a new Tippman Model 98 for $126. The M98 is a little more rugged, but it is also heavier and can't be field stripped nearly as quickly. It's a decent starter gun with some potential, but I wish there were more aftermarket upgrades from other manufacturers. An upper level Spyder (a TL?), a Tippman Model 98, or a Piranha are good alternatives.