My best pal turned me onto recreational Viagra. Both of us are pretty well informed on the usage, if not the dangers, etc.
First off- don't use a whole pill. Ever. If you have no erectile problems, don't waste the whole $10 pill on one sex period, you absolutely don't need to. You can generally cut the pill into 3-4 sections and use one each time, and still have the effects. I've been using the same 10 pills for a couple years now! Granted, I only use the pill when my daughter is at the grandmother's house or something, or it's a special "Really want to go all out" type night. It's incredibly rare.
Anyhow, the effect on me is pretty good- after about 15 minutes, just about any contact in the penis region will give you a very firm hardon, and it'll stay for... well, pretty much as long as you like. The first time I tried it, I had to eventually call the dogs off for fear of leaving a sore, battered girl behind.
Hard as a rock! My buddy didn't last any longer with it, so I guess results will vary, nothing could get me to come unless I tried REAL hard the first time. (Granted, I took the whole pill that time)
For any guys with a doctor who HAVEN'T tried it, I highly recommend asking for a free sample. Complain about how you've been working so hard lately, blah blah, whatever, and they'll likely sock you with a 6-pill sample pack- that's about 18-24 uses for a healthy penis. Can't beat that! And if you don't like it, or the experience doesn't befit you, you're not out any cash.
Also, I recommend going out and grabbing a box of "Vi-gel" for your girl/wife. This is a topical gel you put about a dropful of on her clit prior to lovemaking- again, results vary, but when it works, she'll appreciate the effort! It's not too expensive, and can be purchased at some Wal-Mart/Target types over the counter. It works! My wife has never tried the pill, though.
Good luck and good sex!