Metamask does what it says but it's annoying and painful to use. Especially trying to log into your account. Metamask recommends that you log out of your wallet when your not using it which is good advice as you don't want to tell everyone how much you have. However, it virtually impossible to log back into your account with a simple cut and paste of your 12 secret words and passwords. Let me explain...
First you copy your 12 secret words to paste into the box. However, as soon as you click anywhere else to paste your password, the metamask window disappears. When you open it again, it's asking for the 12 secret words again. So, your only option is to paste in either the secret words or your password, not both. One of them has to be done manually to keep the window open. Another frustration I had was when I recovered my wallet after it logs me out is after I had pasted in my 12 words, it asks me to create a new password. Now this is supposed to be a strong, secure password and I like to use at least 12 digits. So I create a new password but as I type it in, all I am seeing is the common security dots so I can't see what I'm typing. This means I can't type it twice like it asks and I can't copy and paste it anywhere. The fact that the Metamask window reverts back to the start whenever I click away from it and have to open it again makes it almost impossible to use conveniently using cut and paste.
One more issue I have with Metamask is, whenever I close my browser, my settings delete history and cache. This means I have to recover my wallet every time I open my browser. It also means I lose all of the account names and have to enter them again.
This is a great app but the user interface is a nightmare and needs to be sorted. Metamask NEEDS to be able to save your settings even if you clear your cache.
I'm giving Metamask a 2 star rating only because it does work once you work out how to enter your information without the ability to cut and paste