Spermicide can cause irritation for one or both partners, which is why we usually suggest using non-spermicide condoms in conjunction with hormonal birth control. That way you get double protection against pregnancy, but don't risk irritation to sensitive genital tissue.
Also, this should really be obvious, but spermicidal condoms taste absolutely awful, and shouldn't be used for oral sex. That's why they make yummy flavored ones.
And even if the condoms are lubed, as most are nowadays, it's a good idea to use additional water-based lube, like Astroglide or KY anyway. Not only does it make sex feel a lot better, it helps to keep the condom from breaking from too much friction.
You might also like to check out the Safer Sex: Condoms, Lube, and More forum for more advice on condoms and such.
"The only unnatural sexual act is that which you cannot perform." - Alfred Kinsey