I worked for 2 years with Slate in their engineering organization and it helped set me up for a big career move. Its a fast paced work environment, technologically quite advanced and enormous opportunity to be part of a creative team that is at the forefront of it all.
Lots of learning opportunity for me that helped me shape my career. Fortunate to work for some credible leaders in the engineering organization and learn from them. Its a wonderful team that I am still in touch with and quite thankful for the opportunity.
Cons
Fast paced technically challenging work environment. Its a boon for many and if one is not up to par you may not fit in.