I'm using it regularly.

The main reason I switched from WhatsApp was indeed the buy from facebook - I looked around and found Telegram to be a viable option.

So far I communicate with a lot of people via Telegram - altough they use Whatsapp too. The main issue is "Hey, have you got WhatsApp? - No. - What??" and while explaining Telegram, I find that the very reason I switched is not much of an issue for the others.

Other reasons I switched:

Desktop client

At the time I switched, there was no option to write a WhatsApp Message from my Computer - and since I'm sitting before this machine 80 % of my time, it was inconvenient to scram out my phone, type on the tiny keyboard, put the phone back into my pocket/onto the table and repeat until frustrated ^^ I needed some other means, Telegram delivered. With (now) Native Linux/Win/Mac Application and even a Commandline version - I'm pretty satisfied.

Open API

As a person who programs a lot, this was very interesting - doesn't matter much to non-programming folks, but to me it is. Why? Someone made an Commandline-Interface for Telegram, someone else made a Chatbot with that Commandline interface, I adapted this project for my personal needs (Calendar management of my band - who is away at which date etc.) - I'm free to do such stuff! And thats amazing. So is the creativity of other people - I don't need to be a programmer to enjoy such stuff.

Security

Private Chats between peers, which happen to be encrypted - nice to have. Although I read somewhere, that the encryption (MTP Protocol) is weak in a way, it's better than nothing.

I'm looking forward to more features and stuff, to make more people switch to Telegram. The ultimate thing would be (for me) a self-hosted Telegram-Server, which I can integrate into my normal App - so I can have e.g. Company-Intern Chats within the same App as my other Chats (think of Slack - but integrated)

I'm sorry for the missing sources, I didn't have the time to search everything.