Him Indoors and I both swear by our home made, laid in flemish twist fastflight strings. They need fewer strands (as all of them go round the limb tips, not just half), and only need serving in the middle.
Its very theraputic making them, they last forever (Him Indoors still has one he made in 1991 and it has never let him down) and they look reaaaally cool. They take a little longer to shoot in, and can be a tiny bit slower than running loop strings, (they don't affect my sightmarks significantly) but they are easy on your limbs too.
However, they take time to make so Him Indoors has a HNL one bought second hand but new from Tarkwin (thanks) which he really likes. Much better than the previous bought one he had. I have a generic one from Bowsports and I don't like it much.