Tiger Moth automatic slats worked very well and saved many lives including mine when ham fisted students turned steeply onto finals that could, on occasions induce a flick stall, Megan's comments about Chipmunks and Austers not having stall warning devices fitted is true but these aircraft fared well because they had flaps which the Tiger did not. When slats were wired up the accident rate went up. It was not so much because of costs but more to do with poor Pilot procedures when not locking slats when carrying out aerobatics etc.
Slats were a lifesaver in their day and still are on many modern jets.