I have now exhaustively tested the Aurifil 50wt thread for hand sewing with all of the English Paper Piecing I have done during this holiday. For anyone wondering whether to give this thread a try, I would highly recommend it and you won't look back once you do. Having been a dream for machine piecing, it has been as much a dream for hand piecing.
What makes the difference? It glides through the fabric like butter without snagging. It also glides back out again when removing basting stitches. It is fine so makes nice crisp seams but is also strong so doesn't snap when you yank on it hard. It barely tangles at all and, when it does tangle, it untangles easily because the tangles just slide out.
Because it is strong and glides through the fabric, I managed to try a new speed piecing technique which I've never used before. I load about three inches of whipstitch onto a short section of thread and then drag the whole lot through in one go. I tried this with another thread and it was not smooth enough to work.
I would say I can hand stitch at least twice as fast with Aurifil as with previous threads I've used because of how wonderful it is to work with. Any questions, let me know and if you'd like me to show you how I speed whipstitch, just let me know.