i don't use a seam ripper anymore...I much prefer a very sharp pair of thread snips w/ thin blades. I started using them when i worked in a factory making firefigher uniforms...Snip every few threads and pull apart - easy peasy..
The ones we used at the factory was from Wiss - I saw there is a pair from Fiskars at JoAnn's - the key is to look for a thin blade w/ sharp points to snip the thread.
I was looking for a picture:
http://www.drillspot.com/products/39...ead_Shears?s=1
If you google 'Wiss Thread Snips'. you'll find several places that sell them and probably cheaper - but they're worth the price
ETA: Gingher has a pair that looks similar DO NOT get those - the blade is too thick to snip the threads - great to cut thread off the spool, but not to snip threads to rip out