I have been using Embird for about ten years, however I don't digitize but i use the heck out of the basic program. I do a lot of combining designs, spliting designs, correcting designs and resizing designs. You can download a trial of Embird Studio but it has many limitations, like printing or saving you design.
But, the real reason I'm replying is just to make sure you know about Sadie Sews, that site has a free digitizing program you can download. I think if you put Sadie Sews in your search engine you should be able to find it. It might not have everything you are wanting in a program but it might give a little more insight to what you will want in a more comprehensive program.