The following is my experience/opinion with preseed:

I was on BC for 10 yrs because of endometriosis. When my husband and I decided to ttc we got preseed thinking it would be difficult for us to get pregnant due to the endometriosis. We got pregnant within 2 to 3 months without temping or anything like that. Unfortunately we miscarried (don't worry it had nothing to do with preseed). So when we "tried" again we weren't actually trying, although we weren't preventing anything either so we never used the preseed and just either used nothing or regular lubrication. We got pregnant the first month after we stopped using protection (aka pull out method: hey it works for us).

So, I don't think preseed is as great as it is advertised but if you have been trying and not conceiving I suppose every little thing helps.

i used preseed because i was on clomid and it dried me up in the days leading up to ovulation. but i didn't ever need to use it the day of ovulation, so i guess it could have helped! of course i don't know which days sperm is the one that got the egg!