It might be a little easier to match to 12" if, instead of messing with the warp markers, you go to the tempo field on the upper left of Live and hold down the shift key and use the arrow up and down keys. This will get you tempo increments in tenths of beats, rather than entire beats. But I also can't beat match vinyl for sh!t, so take that with a grian of salt.
The best thing Live djing affords me is the ability to overlay entire tracks over one another in a way that could never, at least with how far I want to pursue it, be accomlished with vinyl. Like laying autechre over Nina Simone. It has a great potential to reframe old music that normally couldn't be used or 'matched' into an electronic set.
At the end of the day, I agree with the above comments about djing: it's all about the track selection and who cares how you got there.
