I recently changed my tranny fluid out with Amsoil fluid and noticed an imediate difference in the shift firmness. Also running 10-15° cooler normal driving, haven't yet towed with the new fluid.
I'm not sure if other filters are better or not but examining the design I beleive the OE is fine. Here is how I did it.
1. Drain oil and remove pan, remove filter(make sure you get the rubber seal out of the valve body, it usually gets stuck up there)
2. Replace filter and pan re using original pan gasket. Fill pan with new fluid, approx. 8 quarts.
3. Disconnect tranny cooler lines from radiator and cooler, blow out cooler with air(you can pull the lines down behind the bumper to get them closer to your catch pan).
4. With the pan under the tranny lines, start your truck and monitor the fluid coming out, once it starts foaming shut the engine off(about 20 seconds).
5. Fill the trans again and repeat the process untill you see new bright red fluid coming out(I put approx. 17 quarts in by this point).
6. Re connect tranny lines, start engine and let run for a few minutes, cycle through all gears. I then drove it a few miles.
7. I ended up putting in an additional 2 quarts to get it in the middle of the full scale for a total of 19 quarts. Exactly what Amsoil says the capacity is.
Note: I recommend sealing the two piece dipstick tube at the joint about 6 inches up from the tranny with some RTV silicone, it allows moisture to get in the tube causing a rusty condition. I even found a little water in the bottom of my pan.
I hope this helps. Its really pretty easy and I am confident I got all of the fluid replaced.