I am the author of that digit recognition tutorial you mentioned, and I would say, that is no way substitute for tesseract.
Tesseract is a really good OCR engine, may be the best OpenSource OCR engine.
The tutorial you mentioned is just a try, to understand most simple working of OCR.
So, if you are looking for OCR app, I would recommend you to use OpenCV for preprocessing the image and then apply tesseract engine.