In reply to Laubie:
For things like windproofs, and anything with a membrane, detergent blocks the holes in the membrane, so it doesn't work properly.
Soap is more gentle, so any gear I'd just treat the same, and wash as gently as possible, so as not to cause any damage to the fibres.
I guss with slings and stuff is doesn't matter quite so much, but a) I'd prefer not to take and chances and b) a packet of soap flakes only costs about 99p, so is probably the cheapest option too.