- the option to select multiple files
- a more user friendly gui (the fact that it works with most people is not an argument, I had to open ports and add gateways for it to work = not very user friendly)
- command line only for developer reasons, if you want mass adoption you don't want the majority to have access to something they don't understand. It scares them away.  
- the ability to upload files larger than 500MB
- Progress: a solid team working on sia, moving forward in a professional way with enough transparency.  
- trust, if you want me to store my files I need to know or at least have the absolute impression that my files are safe. This is a beta, which means they aren't. Most people will likely only store (personal) data with a final product that has had some 'testing', has been reviewed, troubleshooted, benchmarked,...etc.
 
I will however store some data that is 'a little less important' to get the ball rolling and support this community. Community, also very important!

Keeping in mind this is a beta I know everything needed will be added once it's ready. But you asked, so...  

edit: the ability to lock my wallet and make backup directly from gui instead of having to copy it out of the folder.