Based on my friends, mostly foreigners and English-speaking locals here in Hong Kong, Signal has grown about 20% in the past week.
https://twitter.com/signalapp/status/1349577579091566592
https://twitter.com/elonmusk/status/1347165127036977153
edit: as daniel_sk points out this is not a x5 increase but crossing the threshold from 10+ to the next 50+ mm downloads.
I will continue to use iMessages for my iOS contacts. For SMS people I will gently nudge (hey, have you tried Signal? and then let the convo go where it does) and then use Signal as the primary for those people.
99.9% of messaging (for me) occurs via iMessages or SMS. FB Messenger is occasionally used for people who are more acquaintances (don't have their phone number).
I don't really have a good reason to not use iMessages (blue bubbles). Reasonably secure and Just Works. SMS on the other hand.... my least favorite part of SMS (besides the complete lack of security) is that media messages are crippled in quality. Photos and videos are compressed and distorted beyond belief.
not just android, they work with every mobile handset even with the poorest reception or (even lack of) data-plan.
i use ~200 sms per year, pretty constant since i got my first mobilephone.
kinda sad we didnt come up with something better thou.