I was in Bangalore the week (and night) that it went down. Absolute mayhem once ATMs etc. opened up, but the locals that I spoke to were actually really happy that Modi had done it, even if there was some short term pain for them, and the lower classes. They did seem to think the poorest folks wouldn't be too impacted as they were unlikely to be holding 500 and 1,000 Rs. notes.
I rarely use/have cash in India, but I had taken out 2,000 Rs, which came as 4 x 500 Rs notes, on the afternoon before the evening this was announced. I had some Aussie colleagues visiting with me that did the same, though they had taken out significantly more than I, as they were on their first visit and wanted to do some shopping, etc. After hearing the news, they straight away (and quite cleverly) used the cash to part-pay their hotel bill, before the clock struck 12 midnight, when the currency would no longer be accepted. They later claimed that payment back in their expenses.
I had one of my staff convert my few 500 Rs notes for 100 Rs notes a couple of days later. Our company somehow managed to get a Bank to come into our city office with a portable cash exchange set-up. They had to install temporary CCTV and everything in the room. It was quite impressive for what it was. They were in a meeting room opposite to mine, and the staff were queued up to that door the whole day! We have about 1,000 staff in that office.
Cheers,
Matt.