They are my "go-to" needle for most piecing & quilting. As far as machine needles go, Microtex/Sharps are the sharpest, thinnest needles out there in each size (be sure to match the size with what your thread manufacturer recommends -- I use size 70/10 with Aurifil 50/2 and size 80/12 with Aurifil 40/2 and 28/2). They are especially great for batiks, but I really like them with any fabric.
I prefer the Schmetz brand because their needles are all color coded so even if I forget what needle I have in the machine (size & type). I have also used their Quilting needles for quilting. I like the rounded Quilting tip for certain fabrics that have a looser weave like repros (for regular fabrics & batiks, I use Microtex for quilting, too). And, of course, I've also done regular clothing & home dec sewing on it, for which I use other types of needles. Here's a link to their color chart:
http://www.schmetzneedles.com/schmetz-color-code-chart/