As a product, I hear that Twilio is great. But from what I've read, after their IPO last year, the have to close large Enterprise accounts and are having trouble. Amazon eating their lunch is not good news either. Also, is Twilio still using AWS?
Their stock isn't so hot right now but that's not terribly out of sorts for a relatively new company. Enterprise I've heard many stories about. Their commitment to starting with the developer is admirable though.
Disclaimer: I do own some Twilio and several other telco stocks (but I still believe Twilio is way overvalued and buy on dips because a large carrier will eventually buy them out so I'm willing to go for the ride), but I make more money from companies dumping Twilio/Nexmo/Plivo and going with custom solutions.