They are not very effective, compared to bc pills, diaphragms, or even an IUD.

You should only use a spermicide alone if you are 'okay' with an unwanted pregnancy.

Spermicide is not as effective as many other methods of birth control that are out there. Spermicide does not do well on its own, but it makes a great back up method for other forms of birth control.

"How Well Does It Work?

Over the course of 1 year, about 29 out of 100 typical couples who rely on spermicide alone to prevent pregnancy will have an accidental pregnancy....Spermicides are most effective when used in combination with another form of birth control....

Possible Side Effects

Spermicides may irritate the vagina and surrounding skin. Another possible side effect is recurrent urinary tract infections because the spermicide can disrupt the normal balance of bacteria in a girl's body."
http://kidshealth.org/teen/sexual_health/c ontraception/contraception_spermicide.html

So even though there are some side effects, spermicides are pretty safe. They don't have any really nasty, life threatening side effects like many hormonal methods do. I have used spermicides and have not had a problem yet, no infections of any kind.

I used it together with condoms for a while and hated it. It gave me UTI's and tasted horrible. (I didn't taste it directly but you know, things spread ...)

Llewellyn was pretty thorough. Not very effective on it's own, irritating to the vagina. It is recommended, however, for use with a diaphragm or condoms and stuff.