I don't do ultralight, but I have tried a lot of different ways to secure all kinds of tarps, from heavy canvas to the (throwaway) polyeth woven tarps, and these are by far the best way to secure any tarp in the worst conditions you would try to use a tarp in:

http://www.grabbittool.com/catalog/product_info.php?products_id=28

I've tried the through grommet style, the gripclips, the gator clips etc. These here are far superior. They are a lot bigger and bulkier, but they will get the job done.

After shredding three big poly tarps on a hilltop one fall day using rope all sorts of other fasteners, I ran to the sporting goods store and grabbed a couple 4 packs of these and had a tarp up that stayed up through the winds I'd guess at 25 mph consistently for almost two days before it subsided. That last tarp stayed tight and didn't rip out anywhere.

Now I have a box full of these 4" grabbit tarp holders, and another box of these:

http://www.grabbittool.com/RockBuster/RBHome.htm

They too are not ultralight friendly, but I know they work, and work well. I like to use what I know works, and I prefer these to making my own rebar tent stakes, which were truly brute force stake material.

As for whether to use a tarp vs a packable tent, I prefer a little luxury, and a tent is going to afford more comfort under most conditions than just a tarp. I will usually deploy both, using the tent as the sleeping area and the tarp to keep stuff off the head in camp while cooking etc.

Then again, I don't mind packing a 60 lb backpack when I do that sort of camping. YMMV.