Originally Posted by rjtim
Are downloadable apps from Play Store and Samsung Apps generally trustworthy/safe?
No. There are still malwares on Google Play. Always check needed app permissions when you install new app ! It's the best way to protect yourself. One of the latest malwares used another scheme - when you install it, it downloads a separate apk. However you should agree with the permissions of this separate apl in order to install it. So, it's still safe !
If you have permission troubles you can check Anti Spy Mobile Free ot PermissionsDog - they will make analysis of all permissions that are needed by your apps.