i use it. I like it a lot better than trying to remember to check x number of agencies to see what has sold and when.
this way i just open the microstockr app on my phone once a day and see who's selling what.
to my understanding, based on what i read on their website - the login credentials are never sent to the microstockr server. so if you ever 'save your login information' on your phone, or computer browser, its basically doing the same thing.
i was worried when I first tried the app - the same way you are - but i've never had my money disappear so thats good. and none of my images have had their titles changed to "cactus. cactus. cactus. cactus. cactus. cactus. cactus. cactus. cactus. cactus. " and none of my images have been deleted from my portfolios, so I think its all good! if they know how much I sell well whatever. lol.