For me, there is a fine line between perfectly ripe, still very firm, jaboticaba fruits and those that are slightly more ripe and beginning to have give to the touch that Oscar describes. I find that the birds get my fruits during the beginning to soften/give stage. This is one fruit that I can sort of get a jump on the wild life and harvest the fruits while still very firm, but oh so very sweet. My dangling fruit method allows me to do this. Of course, if you beat the birds to them, Oscar's tactile suggestions will get you to where you want to go.
For me the firmer the fruit, the better as long as full maturity/sweetness/flavor has been acheived.