- Teachers can not give you motivation but they can sure kill it.
- An app that keeps people motivated is better than nothing at all.
- Horses for courses (not everybody is the same, and equally affluent, what works for you may not work for someone else) and if people are on a budget and they find a way that can make them enjoy what they are doing without breaking the bank on teachers and piano tuners then that's a benefit.
- With what is available online + a $400 digital piano you can get surprisingly far if you are self motivated, and occasionally spending an hour or two with a teacher (or simply a better pianist) will stretch your abilities further.
- if you feel that you are not comfortable or maybe even are injuring yourself then stop whatever you are doing and ask an expert.
- If you have a goal and/or want to be able to perform and value your time over your cash then a good teacher is the way to go but beware, not all teachers are good.
- if you can afford it, want it and you can find a good teacher definitely go for that.
- An acoustic piano is not a 'must' to be able to learn and practice, in fact, a digital has some advantages (the ability to practice with headphones). Silent pianos exist but are usually quite pricey.
Finally, I'd like to plug http://forum.pianoworld.com/ which is an excellent resource for people interested in playing and teaching piano.
Also, you can have a teacher where the focus is to have fun with it and not drilling boring stuff. That's precisely the conversation I had with my current clarinet teacher. We still do boring stuff but he also brings me jazz songs and classical duets to play according to my level. It's a matter of establishing your goals with the teacher the same way you put them with yourself.