My experience. Am not a medical professional. And I am female, so your experience (depending on your sex, weight, and other considerations) may vary.
Diamox is fast-acting for me. I know this because, back in 2010, after suffering through hours of Cheyne-Stokes at altitude, I took it at 3 a.m., and was sleeping like a baby (finally) within the hour. This suggested to me that Diamox gets in my blood fast. So fast that I do not bother to take it until I reach a high sleeping altitude (no day-before dosing for me).
Caveat: I always build in acclimatization -- two nights at 10,000 or so feet before going higher -- and I don't need Diamox until I am sleeping over 11,000. Further caveat: I do not use Diamox for as prophylaxis for AMS -- though I assume I am getting that benefit there as well -- but to address a specific issue that I experience (periodic breathing at altitude).
I experience minor side effects whenever I take Diamox (I only take 62.5 mg/day, right before going to sleep at altitude). The key side effect that I experience at this low dosage is intermittent hand tingling. I ignore it. It does not interfere with my enjoyment of the mountains, or my physical abilities. It seems to stay with me as long as I am taking the drug (tingling can occur from time to time up to about 12 hours or so until after I stop).
There is a lot of anecdotal evidence on this board, that you have probably seen, of interference of enjoyment at higher dosages. I personally have not experienced the problems described at my low dosage.
I do up the supplemental electrolytes SIGNIFICANTLY while on Diamox. Just in case.
