Best marketing software ever. It's been the main reason for our 2x growth year over year.
This is a long term investment of time and resources. However, now with the startup program, money investment isn't as large.
I can talk about inbound marketing and Hubspot for days but this is one of the few softwares that does it all. If you're considering this I recommend getting Inbound certified and then when you get the product getting Hubspot certified to learn everything you need to know.