I personally don't open them because most of the things in them are worthless, I try to sell them if I am lucky enough because trunks are no longer wanted by many.
If you go to the forum list and click "Gaia Exchange" you will find a "How much for a...?" sticky. Click that, then click GEN, and scroll to the "Uncommons" section. Those can be found in trunks. You will only receive female and unisex items if you are female.
Yes, there are a few decent things in them but that is based on a matter of opinion.
There are Price Guides listed in a sticky at the top of the Exchange forum. Try looking in one of those and you'll see a list of what items can be found in the trunks. 3nodding