One important and rather idiomatic rashii-expression is in describing a perceived seasonal change.
今年の夏は去年に比べて、ずいぶん涼しい夏でしたが特に2週間位
前から秋らしい気候になりました。
But apparently, like you da=appears (while generally still more abstract than sou), it can represent the speaker's conjecture based on something read, seen, heard etc. :?
These are just sentences I've received, though, I can't vouch for their typicality.
この文章すばらしいですね。 That looks like a great sentence.
これが普通じゃないらしいと気づいたのは
かなり後になってからですが
(Although I've noticed that this doesn't seem to be as common after some time (of getting to know someone)).