As with most fruits, the selected variety can be important. Feijoas vary greatly in size and flavor. Most of the Edenvale varieties like Edenvale late, Improved Coolidge (selected by Frank Serpa), are excellent if you can still find them. Triumph and Mammoth from New Zealand have excellent flavor and quite large. So many feijoas are seedlings and of ornamental value only. The selected varieties are worth getting.
I have been drying Hachiya persimmons for backpacking and found that the drying process eliminates the astringency, and they are easier to slice when firm, not jelly-like.