ah you mean EMOTIONAL pain, not physical pain :)
I mean nausea, tachycardia, headache, all the stuff! It's most likely physically unpleasant.
Look into the reports on this site of people who woke up after ingesting it. Or at hospital case reports (although they need to be taken with a grain of salt as any medical intervention comes with its own unpleasant effects).
On the other hand, there was a video of a young women posted here recently, where it looked peaceful.
Any poisoning of your body will cause your body to fight against it. The only thing that can make it pleasant is to lose consciousness before that happens. SN in and of itself has neither sedative nor hypnotic effect. That's why the handbook recommends benzos.
And look at the recommended dosage. If it was just for emotional pain and a little bit of anxiety you wouldn't need 50(!)*10mg Valium!