Add me to the list: I'm a Mac convert thanks to OS X and my TiBook (first generation 400mhz model). I won't go into the OS X side of that story, but I will add a few things about the TiBook that weren't mentioned in the article.
Battery Life - I've been using laptops for over six years now, and one thing I found is that laptop batteries are the bane of all business travelers. The Makers advertise long battery lives; the Users get frustrated when reality sets in. Every Windows laptop I have ever used loses a significant amount of battery life in the first six months and the new slim-style notebooks are notorious for short and shrinking battery life. Not the TiBook. While I have never had the 5 hours advertised, I have had consistent 2-3 hour life ("Forrest Gump" stops just a few minutes before the ending), and that's with using battery power day-in and day-out. Maybe it's OS X's power management, but the TiBook battery is excellent compared to the many Windows laptops I've used.
Ports - On a slim-style laptop, it's uncommon to find two USB ports, a Firewire port, AND an S-video out port. Enough said.
Shhhhh! - This was mentioned in the article, but it's worth repeating. The TiBook is quiet compared to other laptops I've used. The fan is loud, but so is every other laptop fan I've heard and the TiBook's doesn't turn on very often.
Keyboard - The article gave the keyboard a thumbs up, but failed to mention one of the reasons why - the wide screen. Not only is the keyboard firm, comfortable, etc, but the wide screen forces a wide base, which allows for keys that you can actually get your fingers on. Unfortunately, the move to smaller Windows laptops has often meant smaller keyboard keys.
I have to give the speakers a thumbs-down. They don't offer much low-frequency punch and grate on my ears after short listening experiences. Thankfully, the headphone jack is in a convenient location.
I have heard gripes about Airport performance, but have yet to really experience it as I have known wireless access with just my TiBook.
Overall, I love the TiBook's design and performance - but mostly the design.