Once lenient, return policy changes dramatically in Australia and varies between shops. Personally I prefer the Australian way and ready to pay a slight premium for the return of peace of mind. Myers, Dj, Kmart and Big W are the few I like. Other retail has stricter policy. (Edit: omitted Ikea)
How would Return Policy influence your shopping?
It depends on what you buy I guess. For clothing, then I assume some would shop with stores that have relaxed return policies since they can't try before they buy online.
For electronics/electricals, personally I would just search for the best bargain and get it from whoever sells them the cheapest.
Just out of curiosity, why is Ikea's return policy strict? I was at IKEA WA yesterday, and happen to see their 'return policy' ads plastered everywhere in the loo. It seems pretty flexible? They would apparently give you a full refund if you change your mind provided you have not assembled the stuff you bought. Otherwise they'll happily give you a store credit?