http://www.wetwebmedia.com/PondSubWebIndex/pdsnails.htm
Pond Snails, Bane or Boon?
I think this thread posted in first post value of snails thuch upon most of the Yays and Nays.

So would I ?

Well it deepends.
In a aquaqulter operation thats a no, unless I specificly where culturing snails for comercial sale.

As part of a "natural" pond I would say they are wellcome as a part of the chain (native). However I would be wery sceptical to bring in just any snail.
And i also would have second thaughts if I where to use the pond as swimming pool or playground because they atract waterfowl amongst others that prey on them.

So for a specific rason/goal in one pond maybe yes
for other specifics or differente reasons in another pond definetely no

PAUL