I've only been taking alendronate for about three and a half months, and beyond a couple trivial side effects the first couple of weeks -- very sore and somewhat tired the day after first dose (only that day) and two very short spells of extreme dizziness during the first week and a half or so -- I've had no other side effects that I know of.

I worried prior to taking the first dose, especially after reading about all the possible side effects, and put off taking it for a week. Finally decided to, and so far I'm happy with it.