I love that this software is so heavily focused on outbound sales. This isn't marketing software that you can adapt to sales, this is software created and built for sales organizations. That fact is very obvious in the way they implement their features.
Outreach always leads the way in terms of feature innovation, and they continue to offer the best outbound email settings to truly automate your process. You can drop 1000 prospects into a sequence, throttle it to send 100 per day, set it to resume OOO replies after a few days, and set it and forget it. Just set up a schedule, make sure you exclude national holidays, and you don't have to touch it ever again.
Something they also do better than anyone is their task management. I frequently have a task as a step in a sequence (I.e. Connect with the person on LinkedIn), and when a prospect hits that stage it creates a task in the system. This happens hundreds of prospects at a time, but when you start your tasks it takes you into this workflow that lets you call/email/take notes on the action and just click next to take you to the next one. Really lets you get in the flow, and is an amazing tool for inserting a manual task into a sequence that you can still get through quickly.
Some examples of awesome features include:
1) Auto resume OOO
2) Fallback text in the templates
3) Automatically skip holidays
4) Phone call integration so you don't have to leave the app
I don't know that there are any cons. The only one that I can imagine is that when you start fresh on the system, the interface can be a little bit daunting. There are actually a lot of settings, and if you don't understand the hierarchy or what you use for what, it can get very complicated.
Thankfully they have good customer support and a LOT of good documentation, so it's not that bad if you spend some time learning it.