1. Streaming video only.
If you are going to sell me a course on anything. Please consider using something other than streaming video to deliver. My time is very valuable and I don't have 2 hours to watch all your modules to find the one thing I didn't already know.
Consider offering PDF text versions for those of us who are advanced. Not to mention anyone who's second language is english and may need to read more than listen.
I know many will argue on this and say that people will rip off your content but guess what. Streaming video is just as easy to steal as a PDF If Hollywood cant slow piracy don't expect you will either.
2. Making me join your list
I have no problem with list building. In fact I do it myself but there are plenty of ways to auto add me to your list. If I am buying a product I don't want to have to check my email to confirm my subscription just to download your product.
3. Fluffing it up
Most of the products I have seen that take an hour to watch or 40 pages to digest could have been condensed into WAY less. I think product creators and buyers attach too much value to volume and not enough to substance. If you can say it all in 2 pages then say it in 2 pages. If you deliver value people won't refund.
Some of my best products were short and got comments like "You could have written this on a napkin and charged me double".
Don't be afraid to get to the point and deliver the goods. We buyers respect that