In looking for the best online course for piano, I came across three different ones that looked promising:
Each one offers a different approach, and I wanted to know how they compared to each other.
First, Piano by Pattern claims to teach you how to play piano ‘by ear’ in just over an hour. The course bases its content around a series of 9 videos. So lets hope that your keyboard or piano happen to be right next to your PC where you’re going to watch the videos. The ‘promises’ made about this product are such overblown hype, that it should be a tip-off that this is not a plan that is going to work for you. The best thing about this program is its 100% money-back guarantee…at least you can buy it and turn right back around for a refund (and keep the product, for what it’s worth). The 9 videos take up about an hour and 15 minutes, and offer some decent tips, but not enough for you to actually ‘learn to play by ear’.
Any course that promises you will learn to play ‘without the drudgery of repetitious practice’ is exactly what you think: too good to be true.
So the next course, Rocket Piano offers a different approach. The materials are available either online for immediate download, or by mail. Right away this seems ‘less sketchy’ than the previous course. Then the content arrives: 218 lessons in 3 books, 57 video lessons, and 133 audio files…and that’s just the beginning. It’s not overwhelming in a bad sense…it’s just a really impressive set of materials. The lessons are easily printed out to take to your keyboard or your piano. And the content covers all the fundamentals of learning piano…with no overblown promises of playing a concerto in 3 days. 
This package was excellent, and really covered the basics well, all the way up to more advanced play. And it covers all genres of music: Gospel, Jazz, Blues, Classical and more.
The third course, Instrument Master was intriguing. The site actually offers both violin and piano lessons, which can be taken one of two ways. Either the technique for learning to play is so unique it applies for multiple instruments, or there is something wrong. Being a cynic, I immediately assumed that this was more hype than content.
Actually, my assumption was a little mis-guided. It’s not that they think the technique is so special. It’s that Instrument Master is really a service that supplies regular (monthly) lessons. The upside is that you are getting really good lessons, regularly. The downside is that it’s at the pace that they decide, not the one that you set. It would be ok for someone who needed the kind of structure that says, “learn this content by the next date”…but many people don’t work like that.
Overall, Rocket Piano blows the doors off the other two. I thought that my selections would be similar enough to be competitive with each other. As it turns out, there are three levels of lessons…nearly worthless, moderate, and very thorough and complete. (Piano by Pattern, Instrument Master, and Rocket Piano, respectively). Piano by Pattern and Rocket Piano both offer money-back guarantees, which is big in my book.