Well, if by SERE you mean Survival Evasion Resistance Escape, then I think its 100% necessary and useful. If you wanna know how its being used against our enemy, then I can't say anything on that, but how its effectively used on US troops is a matter I can chip in on.
First thing to know, SERE is extremely brutal. Its a physical and mental, more so mental, nightmare. Cold, hot, humid or whatever the temperature, it all becomes nonexistant as the harshness sets in. Lack of sleep, your body shuts down because your not getting enough intake, and of course pain and exhaustion becomes a factor. I took a version of SERE, I did 2 separate tours in Iraq between 2004 and 2008. Actually, most of 2004-2008. I never had to put what I learned into effect, but the point still exists.
The part I'm assuming your interested in, withstanding interrogation, was one of the harder parts. There is no training to give students the ability to torture or interrogate, but I can't say whether or not they could turn the tables and use the tactics to gain information. I never went through the worst of anything, but I neared the breaking point several times. Either way, its useful for US troops. The only thing I can think of thats worse than being captured, is being captured WITHOUT having gone through SERE.