That's not entirely fair given how poorly organized and sloppily written Wotco's rules material often was. I spent a long time reading the monster entries in the Monster Manual and never once guessing that absolutely necessary information on how some monster abilities work was tucked away in the Glossary, which I had never read, and not referenced in the section of every monster entry which said how the ability in question worked.
There are certain disadvantages to being larger, though, especially in a claustrophobic environment such as many dungeons.The flip side of this is, as a DM, I now frequently look into advancing monsters to the next size category rather than adding class levels to them. It's more CR-efficient.