It’s pretty embarrassing when you build up a massive battalion, only to have it cut to ribbons on the offensive, and lose your cities the next turn because they’re undefended. It’s better instead to use siege weapons – like catapults – to whittle down enemy defenses before engaging with armies. Without the scouting skill you won’t know how many foes are hidden within cities, and entrenched units always fight with an advantage. It’s easy to build an army of sword-slinging warriors and throw them at an enemy’s gates, but it’s a seriously bad idea.
Everything has its benefits, and really, you’ll want most of the starting tech anyway.
This is arguably the best discovery, as it provides an explosion of finished technology free of charge. In CivRev 2, one such wonder – hidden on every map’s ocean – is Atlantis. These are structures that, when discovered, provide benefits to your faction – free of charge.