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I very much agree with your assessment of the only two ways to eradicate Poison Ivy. There is one thing you did not mention, something that I have seen for myself: The plant seems to have a built-in survival gene that kicks in when it begins to die. The plant has taken root on the less-than 5-acre property where my apartment building is located; I sprayed at least 90% of it last spring (2011), spending more than $200 on RoundUp Poison Ivy concentrate (one jug "makes" 5 gallons of the stuff). The places i sprayed last year, I sprayed twice to make sure the plants were dead.
The roots did not actually die, and now the Poison Ivy is thicker than it was last year -- and it has spread.
If you have the plant growing in your yard, make sure you are able to get enough chemical spray to cover ALL of it at least two times, and you will likely have to do it again the next year.
If you decide to remove it by hand, you will have to get ALL of the roots/runners/vines, because even a 1/8" section left in the ground is enough to start a new plant.
And if it is growing anywhere in your town/city/county, you will always be working to eradicate it from your yard.
Toxocodendron radicans, the variety that is most abundant in my area, absolutely thrives in open, drier locations (just like its western cousin), and colonies can become extremely large and thick. Where I live, in East-Central Minnesota, there are more and more open, drier areas...