If you're one of the five people (I counted) that have an interest in Overwatch but have somehow managed to avoid the dozens of free trials so far, you'll be glad to hear that a brand new one will be starting up next week. To be more specific, Overwatch will be free to play on both PC and consoles from November 20-26.
In terms of content, you will be able to access the full roster of 29 heroes (including the newly released Ashe), all 19 maps, all currently available cosmetics, and naturally, a variety of game modes. The only thing that'll be locked away from you is the competitive mode, though that's not something you'd want to jump into as a completely new player anyway.
As for whether it's actually worth dedicating your time (and subsequently money) to Overwatch, I would say the answer is a definite yes if you're a fan of team-based shooters. I have a lot to complain about Overwatch and Blizzard does make some strange balance decisions on occasion, but it's still a game I have spent hundreds upon hundreds of hours on, and a game I still love playing. So if you're even remotely interested, I would fully recommend you give the free trial a chance.
You can find all of the details over at the official website, but for now allow me to leave you with an unfortunately small infographic showing the free trial starting times in various regions and time zones.