No problems - but it does grant access to the system files of the phone that you typically cannot see via the phone's menu or other means. So if you are not careful and change or delete or move the wrong file, you can brick your phone.
I have used it successfully to get text messages and photos and contacts off an old LG (5200? 5400? I don't remember) flip phone. If your specific model isn't listed, you can try a similar one to see if it does work. It won't work with all phones.
Hence my caution to use it at your own risk. It's an awesome little program but can be dangerous if you try to do more than just look around and copy files.