I've played it for 110
hrs and still enjoy it.

I can recommend the Vietnam expansion as well. It's basically the same game, but the weapons and map design make for a more intense experience.
The tips:
Remember that the bullets travel and fall, so always aim above the head and ahead of them if your target is moving.
A lot of objectives can be taken out by simply destroying the buidling they are in (no need for plant). This might seem obvious to some, but a lot of people don't understand how easily some bases can be taken.
On Port Valdez, 3 objectives can be taken out by mortar strikes and tanks from afar.
On Arica Harbor, in the beginning, you can take a tank (with improved optics) and nuke one of the M-COM stations from your home base. It might take you some practise shots to get your aim right though. If done right, you will have destroyed it within a minute or so.