I'm gonna post the relevant links. But, if you look at the server list you will see a lot that are running version "SEF / 6.4". The reason is they are using an insane mod!
This mod lets you use your mic to control the A.I (its pretty good, too), it lets you run in very high resolutions, it has the ability to combine SWAT 4 and the expansion missions into one campaign, it has a level editor, it supports a bunch of custom made maps (I'v yet to download any), it has a new mechanic which is a weight system so you can carry more or less gear and be affected by it, it has a bunch of new "realism" features such as "less lethal" opposed to "non-lethal" (I.E stun guns can kill the elderly or kids, beanbags can kill people if too close, etc...) It has new gear and quality of life improvements. Best part? It is essentially a self ran mod, so you can still play the original SWAT 4 and expansion without any of the mods!
Super easy to install, too. Just go to this link:
http://www.moddb.com/mods/swat-elite...elite-force-v6
Extract the file to your swat 4 folder. A new folder will be created called SEF.
Then, update the mod to version 6.4 using this link:
http://www.moddb.com/mods/swat-elite...6x-v64-upgrade
Again, extract it to the SWAT 4 folder and choose to replace the files.
You can open the mod by opening up the new "SEF" folder that was just created. Go to the file "LaunchSEF" and BAM. You're set!
I highly reccommend the server gets swapped to this mod and some kind of announcement made. More people need to know about this mod!