The book learned optimism covers the value of both optimism and pessimism. He wrote the book to help people become more optimistic.
The main thing I learned from the book, is knowing when it is good to be optimistic or pessimistic. There is a time and a place for each. But, on average, optimists tend to win, because they keep trying longer.
I am interested in talking, as I work on ethercalc.
The big issue I have seen is formula calculation speed. I understand render speed is also an issue. I don't know your use case, but the use cases I see tend to have formulas. It is hard to makes formulas fast enough with JS.
The main speed problems with ethercalc are loading the data from the server and calculating the formulas. I did strip down the code to remove these problems to make web apps work.
Web apps as simple as spreadsheets. My aim is to make it easy to add a UI to a spreadsheet. Spreadsheets often have a UI bottle neck. I have seen many spreadsheets that would be much more valuable to business if it had a UI, as more people could use it. So I added UI formulas to ethercalc http://sheet.cellmaster.com.au/examples
Many people want to send e-mail with a spreadsheet. Requests get posted on spreadsheet forums all the time. The same question is posted again and again, week after week. So I decided to create some formulas for it.
Not sure is a big pain point, not sure people would pay, but happy to finish it off if anyone can think of a way to cover costs.
The main thing I learned from the book, is knowing when it is good to be optimistic or pessimistic. There is a time and a place for each. But, on average, optimists tend to win, because they keep trying longer.