The bad points come to light if you're looking to do all the extra quests. For a start it doesn't tell you exactly when things are available...

It doesn't go into detail in how to defeat the Emerald and Ruby Weapons.
Nor does it tell you when the its best time to visit the crashed Shinra Submarine (you can miss out on a not-too-vital fight against Rude and Reno otherwise!)
If you want to get all the Enemy Skills then you need to keep checking the bestiary - rather than telling you when the skills are first or easily available! Not helpful if you've missed your only chance to collect a skill!
It's not very detailed with betting on the Chocobo Racing - where you could get the Sneak Attack, Gil Plus, EXP Plus materia!

If you want to complete this game to it's fullest, then you need to know exactly when side quests are available, when to gain Enemy Skills, when to do the chocobo racing and gain a Gold Chocobo - otherwise you could miss out on many smaller elements to the game. The EXP Materia, for example, is a time saver when it comes to trying to Master all your Summon Materia, so you can gain the Master Summon Materia... and so forth!

It's quite annoying that the official guide isn't that deep. I do feel rather let down that the games creators have created something so shoddy. Thankfully the game is ten years old and this guide has been banging about the same time - the wonders of the internet and all FFVII fans have taken their time to create indepth guides freely available to download!