Free weekend just ended + sale going on, meaning most likely you would be playing against a lot of new players.
Personally, with what little time I did spent on the free weekend, I'm disappointed, because I was expecting the new and improved vanilla tf2. Superficially, Overwatch resembles tf2, but really it's first person Dota, but only the late-game portion.
Overwatch is 6v6 only, and games are way too short. As a result, practically everything you are doing is important. If you die you have to wait 15 seconds and spend another 20-30 seconds walking back to the objective, out of what could be potentially a 6 minute game. The short game time is not really an issue in itself, but rather the downtime waiting for the Play of the Game to finish, commendations, and matchmaking.
Just like Dota, what heroes your team has practically determines how the game will end up, with support being the most important role. But just like Dota, nobody wants to play them. If you don't have a healer, prepare to lose. The most engaging and mechanically satisfying heroes that everyone keeps picking are of course, the most useless. If the enemy has Reinhardt and 2 other tanks and you don't have Reinhardt and 2 other tanks, prepare to lose. One would think that that the counter to a tank would be a sniper or a stealth hero, but that's not the case.
I would say if you enjoy tf2 as a casual game, then this isn't worth it. If you enjoy and are good at Dota and CSGO, or like CSGO but with less importance with accuracy, you're pretty much at home.