As for the trade itself. So far, I'm fine with it. Based on what I have seen so far, Duchene is an upgrade over Turris, who it appears that the Sens didn't want to commit to long term, and the rest is a collection of futures that right now look snazzy on paper but who knows what they will be. Bowers was a late 1st round pick. Those guys usually end up as 3rd liners. Not saying he won't be more, but that's generally where they end up. Based on what I know of him his ceiling is a 2nd line player. Obviously that can change.
Conditional 1st. Who knows who or what this will be, but I think it's safe to assume it will be a 2019 pick.
3rd round pick. If I'm not mistaken, around 20% of 3rd round picks play more than 100 career NHL games. Colorado might make a genius pick, but the odds are against them.
It's too early to judge the trade because of the unknowns with Bowers and the picks, but for right now, the Senators got a guy who is playing like a very good 1C, and a very good 1C is damn near impossible to get unless you draft one, so yeah, I'd do the trade again if I was GM of the Sens.
Edit: Colorado obviously got more from Nashville, which from their perspective puts the trade over the top. But from just a Senators perspective, I'm happy with the trade.