tart berries: when ripe?

So, the more mouth-puckering berries out there: sea buckthorn, aronia, even autumn olive, how do I know when they're ripe? Is it a texture thing?

Oh, this could also go for the ribes family, gooseberry, currant, jostaberry.

??

In general I have found the berries to be ripe when they slip easily off the stem, smell rich and have softened slightly and reached their specific mature color, much like a melon

+1 on what Leah said.

Some fruits will never get sweet according to the kind of sweetness we're used to.  Aronia berries aren't called 'chokecherries' for nothing! 

Some taste better after a frost.

Many of the less popular fruits have uses other than eating raw, such as jams, wines, etc.

Sue