X50,
I've heard this. I don't know that is't true, but my impression was that the anti-androgenic effect is relatively weak that would not be nearly as effective at blocking DHT as finasteride.
There may also be problems with long term use of cimetidine. It's not recommended that anyone use Tagamet for more than 8 weeks at a time. The main effect, H2 blocking, might create problems if you don't have a medical need for it.