I'm using them at present and find they're OK. My main (gigging) accoustic is nylon strung, but I use them on my steel strung jumbo so that I don't have to worry about changing strings too often on a spare guitar.
Being a big-bodied guitar, the dampening effect of the coating isn't really a problem and I still get (to my ears) a full ringing tone.
D'Addario EXP26 cost me £12 with spare 1st & 2nd strings plus a string case, so not too expensive.