@Justin: "How do you find the durability with that stuff?"
I have slept in many versions of the hobo tent, from hardware store tough-plastic tarp, to garbage bags, to the clear plastic that is currently my favorite due to cost, weight, and ease of use. I have never had an issue with durability, but granted, I have not gone more than a week using them, and when I did use them several nights in a row, it was the heavier and tougher hardware store tarp.
@Jamie: "Plastic shelters – yes you can't beat the price, if you want to save the most coin go for it, but a plastic shelter has a life in trips not years (my experience as a kid). Wind is the enemy. Granted protecting a plastic shelter may be a skill that I have just not learned yet."
Of course other material is going to be tougher, but you might be surprised at how tough plastic sheeting or garbage bags are, within reason of course. I have slept very dry, comfy, and cozy in both wind and rain. Wind is only the enemy if you don't pitch it properly. Keeping it low to the ground helps, as does pitching it in a good location where you have small hills and/or trees around you to absorb the wind. Rocks are free and plentiful in most terrains, so as long as you put enough to anchor the plastic right, you should be fine unless there is a storm (and most tarps would crumble during storms anyhow).
Now as far as life in trips, that I will have to get back to you on. In the past I used primarily hardware store tarps, and for years of overnight to week-long trips on the AT I used the same tarp. Then I moved to Sweden and bought a few of the same hardware store tarps to mess around with, and had no need to replace them after many overnight and weekend trips. About half a year ago I started to experiment more with garbage bag shelters and then the clear plastic shelters. I have made several and used them, but the problem is, I am a member of a camping club and my fellow members have been very interested in these shelters so I have ended up giving away several after using them once or twice.
Just yesterday I met up with a friend who is in the club and he wanted one of these hobo tarps, so I gave him the new one that I made for myself. I recently ordered a bivy, and plan on using it with a hobo tarp. I will use the same one and keep track of any damage and/or how long it lasts.