For someone who knows what they are doing they are relatively small but still worth the minor trouble it takes to set them up.
1) The major advantage is multiplayer. This still requires the 1.2 tables or it bugs your about hacked tables. You can play multiplayer easily by making a new folder for it and play it without the media VPs.
2) When playing campaigns like Shrouding the Light which require files from other campaigns you no longer need to move files from FS1 port into the STL folder in order to allow it to find them.
3) You can turn off the media VPs for a mod with quick edit of the mod.ini file when getting errors in order to check where the fault lies. If you're playing the main campaign simply clicking the no mods button turns them off so that you only have the retail VPs to contend with.
4) The mod.ini can specify the image and text displayed in the mod details section of the launcher. Minor but pretty
5) You can specify links to any two websites in the launcher. That can actually prove quite useful when it comes to mission release. You can have the campaign actually link to the support thread here on HLP so that people know exactly where to go to get help.