As someone that works out regularly, I've found ED drugs decrease my workout performance. This is something that happens to some people, unfortunately it does to me. That's one reason I prefer Viagra over Cialas. I want the drug out of my system faster.
It's been found that Viagra persists for most people for about 12 hours, not the advertised four. I've found that to be true for myself, meaning I can handily go for round two, or even three, up to 12 hours later, but as long as I've got over 12 hours in between initial dosing and my workout, I feel no negative effects.
For side effects I do get some nasal congestion. My doc said headaches are common, and the first time I used it, I took the 100mg tab, and yup, nasty headache. Took 25mg the next time, just as hard, minimal side effects.
The four pack at Costco is $43 including fees. For me, that's $2.68 a boner. My drug plan covers it, but even if it didn't, that's reasonable.