I have experienced all three.  I recently posted 2 messages on the San Diego discussion board about this.  My experiences follow: I've used Viagra for several years.  It's generally reliable for one pop, gives me a moderate headache and upset stomach, and costs about $10 each.  The second time I used Cialis, it gave me an excruciating, long-lasting headache, so I'll never use it again.  My favorite is Levitra, available for $10.15 at a pharmacy (name forgotten) practically next to Farmacia Castaneda just across the border, in TJ.  It made me repeatedly hard over a period of many hours, yields an intense, extended orgasm, and leaves NO side-effects.  I hope your experience with Levitra is as positive as mine.  Good luck.

Try taking a couple of tylenol at the same time you take the viagra.  It should prevent a headache.

Have used Viagra w/ the usual side effects, but have never used Levitra or Cialis,, my question??? Is it legal to buy this stuff in TJ and bring it into the USofA? Thanks for any info!

I used Levitra (20mg) for the first time today. I realize one experience isn't much to go by, but I'll report my experience for those who believe in small sample reports. Overall it seemed very similar to Viagra.  I took the advice above and took tylenol with it.  No headaches or other side effects, however Viagra doesn't always give me a headache either.  Calais gives me the worse headaches, but headaches are the only side effect I get from any of these products.  As with Viagra, using Levitra my first erection was very strong.  Seconds were possible today, which for me is about 50/50 when using Viaga.  I'd use it again.  I might also try taking 50mg of Viagra initially and another 50mg of Viagra before round two.  I think I'll make a habit of taking Tylenal togther with the Levitra, Viagra, etc. in the future.  

In reponse the the question about bring Viagra, etc. back in the US.  I've brought a variety of medicnes back without an Rx and at worst just got a lecture about getting an Rx in the future.  I think an Rx from a Mexican doctor is adequate, and that should be easy to get.  I always declare my meds under the theory that the worse that can happen is I'll be out a few bucks if I run into a Customs Inspector who is having a bad day.