What are some thoughts on the Slav Defense

I think it is okay at best. I prefer the French Defensive a little bit more.  

Already the Slave Defense (1. d4 d5 2. c4 c6) White can play the exchange variant which is even more annoying than the French exchange.

Otherwise it's an interesting opening that's quite played by lots of Gms.

Lots of top GMs have trusted the Slav.

If you play the French, then I would suggest you the semi slav instead of slav since it's more natural to play for you. That being said, slav is a decent choice and a trusted weapon of a lot of GMs

Hi!

If you play the French defense against 1. e4, then perhaps either the Semi-slav or the Orthodox defenses would be a good better match for you, since in all of them you have the light square bishop behind the pawn chain.

The typical Slav player likes to have this bishop ready to go to f5 or g4 before moving his pawn to ...e6. At least this is how I play it, and try to follow the same idea in other openings. For instance I sometimes play Caro-Kann against 1.e4, Slav against 1. d4, and the London as White, because all of them share the same idea of playing the queen's bishop outside the pawn chain.

Good luck!

IMHO the Slav is probably the single most underrated opening in chess, and were it not for the pesky Exchange variation, I think it wouldn’t even be close. 
I still think the NID is the best way to play against 1. d4, but the Slav is T2nd in my mind, along with the Grunfeld, Semi-Slav, and QGD.

Ever since I have picked it up, I have loved it. It is VERY annoying to get hit with exchange variation, easily more than the french exchange. In fact, the exchange slav (if I am correct) is the most drawish opening.