In our campaign we counterspell all the time, at least when fighting casters. This is a pretty lengthy and ongoing campaign, and we're at 19th lvl. The opponents we fight can dessimate the party if one of their spells goes off and a few bad rolls are involved, so counterspelling becomes critical. We have both a sorcorer and a wizard in the group, both have all the counterspelling feats available and one even has a Ring of Spellbattle (from MoF). Ussually, during a battle, one of the casters will take up "counterspelling duty" while the other casts offensively. That way we can try to shutdown the most powerful enemy caster while keeping our offensive power pretty high.
Keep in mind, all it takes for an opponent caster to destroy the party is one Wail of the Banshee delivered at the right time and most everyone keels over (we're often fighting Thayan Wizards with the prestige class, so the DC's are pretty damn high). Anyway, for us, counterspelling is one of the reasons we're able to survive these encounters at all.
Keep in mind, all it takes for an opponent caster to destroy the party is one Wail of the Banshee delivered at the right time and most everyone keels over (we're often fighting Thayan Wizards with the prestige class, so the DC's are pretty damn high). Anyway, for us, counterspelling is one of the reasons we're able to survive these encounters at all.