As many forumites will know from my past crazy stories about my long running campaign, it focused on a core group of SF-type PCs and important NPCs. But the PC commander Major Po actively sought out and recruited SF types for his team where he could, and they weren't easy to find. Many important roles in his team were filled by characters who didn't have an SF background but were very good soldiers and were given additional training where possible by Po's SF personnel.
I'm not sure that SF troops would have survival rates that much lower than other troops. Sure they get sent on very dangerous missions but they are also damn good at what they do and they are some of the toughest and most resourceful troops. I think their survival rates would be on par or even slightly higher than line infantry.
In an RPGing context, having an SF-oriented campaign is all about balance in my experience. Sure Major Po's group were hard core killers and tended to utterly dominate similarly sized and equipped opposing forces, but they also attracted a higher quality of opposition too. In my campaign from Krakow onward Major Po's group were being actively hunted by elements of Spetznaz, the GRU and even the CIA. And once they made contact with Colonel Richard Stark from the DIA they were tasked with some horrendously difficult missions, they prime example being their (successful) deploying of a backpack nuke at WarPac Reserve Front HQ in Lublin.
In my campaign the CIA started a program in 1996 aimed at detecting and preventing any military takeover of the US Government in the event of a global war. This would seem like an act of prescience and in fact it was (a result of one of the great successes of Project Stargate
http://en.wikipedia.org/wiki/Stargate_Project). Major Po was one of a team of 12 US Army SF and Intelligence officers and NCOs who were recruited by the CIA and placed in positions in the US military where they keep watch for signs of a military coup. That is why Po (originally a medical doctor) went from being an FBI forensics agent to being comissioned as a US Army Green Beret captain. His SF and officer training were fast tracked but the escalation of the war prevented him from receiving all of his training and that is why he didn't have jump wings.
After the TDM in 1997 Po decided that CivGov was responsible for the destruction of the US and he went to the DIA and told them all about the CIA project he was involved in. After that the CIA went to a great deal of effort to have him killed. In my campaign there were some really vicious CIA vs DIA stoushes that continued right on into the Armies of the Night module.
I think that if a GM allows a player to have an SF-type character it should be on the condition that the player puts some effort into researching the role and playing the character appropriately. The players of SF characters in my campaign had very complex back stories and tended to be played (IMO) appropriately.