Looks like a useful tool.
The plagiarism thingy is a bust though, it seems designed for papers not run of site articles.
I ran an article submitted to one of my sites today and it found nothing wrong on the plagiarism front but I know it has been indexed in at least 46 other places on the interwebs.
To the OP, if you are using The Best Spinner and English is not your first language you are going to be handicapped by your lack of skill at English. If you are going to succeed with spinning you mist be able to see when something is right or wrong AND know how to correct the wrong stuff.
I'd suggest that you might well do better to write one-off articles and submit the same articles to many sites. Just send it to Ezine articles first.
I reject spun content all the time because it is simply not good enough. The same submitters sent me unspun material and I publish it because it is better than their spun stuff.
If you MUST spin stuff then do so when the quality of the content does not matter - although quality should ALWAYS matter to you.