Had the same general experience as you:
1) had definite symptoms of low T before the diagnosis
2) Fatigue after meals, night sweats
3) Initial positive "surge" after the I/O followed by a decline
Not sure I'd be functioning at a high level if not for TRT. No regrets whatsoever from my standpoint. I will say that it has been a challenge to get the medication "just right" -- in fact, this is still a quest after about 16 months on TRT.
I waited about 4 months before doing anything about the low T...very bad time for me.
7/2010: stage 1B mixed NSGCT. Left I/O + 1X BEP. TRT (pellets). All clear as of 8/2012