I played this through 3 or so times before i even knew there was a walkthrough. i spent 100s of hours on my third playthrough and thought i'd done everything. Untill I read the walkthrough. There was a few things I'd missed. Soooo yeah, i'm all for walkthroughs after you think youve gotten everything and done everything. But as far as the official guide goes it was a rip off with the play-online thing, a cheap underhanded way to get hits on thier site. I dont think playonline has the information anymore anyway so although i cant say which exactly is the best walkthrough out there, I can safely say use an online guide like gamefaqs. If you want the sidequest information (and a lot more try here.
Final Fantasy 9 / IX / FF9 - Walkthrough, Cheats, Wallpapers, Music, Videos
and for other fascinating and helpful tips check here. Main Page - The Final Fantasy Wiki has more Final Fantasy information than Cid could research

hope this helps.:mog: