Summary: It works with my wife's iBook G4 1.33 GHz that originally came with only 512 MB memory. My wife typically opens several apps in background, and iBook used to crawl when switching between different apps (access harddrive, wait, wait, wait, access harddrive, access harddrive, waaaaaaaait, ad infinitum). With this additional memory (1 GB + 512 MB = 1.5 GB total now), switching apps is much snappier than before.
Summary: I was a bit worried that it wouldn't work in my Powerbook 12", 1.5Ghz but it worked immediately and installation was a complete breeze. Compared to what Apple charges for their Samsung RAM ( they don;t make it themselves after all) I saved well over $100.
Summary: I bought 2 of these to boost my old Mac PowerBook G4 (15", 1.5GHz). They worked like a charm, it can now smoothly handle the latest Leopard Mac OS, as well as many applications simultaneously. I've had them working for 1 month now, and had zero problems. When I bought them, the Amazon price (about 50 bucks each) for these new RAM modules was almost half the price offered by the manufacturer's website.
Summary: As a computer professional, I've purchased many Crucial Tech memory upgrades for a variety of machines, new and old, laptop and desktop. This particular product works like all others I've purchased from them: flawlessly. This is expected, since modern RAM chips are easy to produce and should rarely cause a buyer any trouble, regardless of the vendor.