I guess it depends on what your budget is and what your taste in furniture is. Ikea, in Innaloo is cheap and cheerful. Although it's not particularly original its practical and offers some really good storage options.
For something a bit different check out Asian Origins on Guildford Road in Guildford (heaps of beautiful Oriental furniture) or Chapels on Whatley Crescent in Maylands. Guildford also has some good antique shops if you prefer lovely old furniture pieces.
Yes,m Chapels has some beautiful furniture but very expensive -I could only afford a coffee and cake.
I was told years ago that Ikea furniture does not last and is not good quality -my partner had it when he was a FIFO worker, and apparently most of it fell apart after several years, so I would now not buy big furniture there.
We are really spoiled for choice. We can get things that are cheap (but then the price is quality) or something that is quality (but the downside is price). I think the best is in the middle which seems to be what Harvey Norman offers!