It's a personal choice. I banked my own. They refer to it as autologous donation.
I gave two units one week apart about 2-3 weeks prior to my scheduled surgery date, which was moved.
Having been pretty symptomatic pre-surgery, it tired me out quite a bit, but other than that it was no big deal.
They will give you iron and folic acid to try to bring your hemoglobin back up faster. Iron causes some mild discomfort in that it constipates you and can irritate the stomach if taken without food. Nothing major.
Aside from personal philisophical reasons for doing so, there is one solid reason I am glad I gave my own blood.
My surgery was bumped once, but they wouldn't bump me twice because my blood had a shelf-life of 35 days. After that, they would destroy it. It seemed they were very concerned about doing that. I suppose it would've been quite wasteful and possibly inflicting unnecessary stress on a patients body.
I do not know if all hospitals act this way as a policy or if it's a policy of the Canadian health care system or if that's universal.
Aside from personal reasons (knowing the blood is safe, not taxing the blood system), I believe this was an important side benefit to my donation.
Incidentally, I was told they didn't have to use any of my blood.
Kev