Yes, though never enable strict mode (in JS) unless you know exactly what it does. `use strict` causes some subtle semantic shifts that can be easily overlooked. For example, there's no dynamic binding between the `arguments` object and a function's arguments:
((x)-> x = 2; arguments[0] is 1)(1) # true
((x)-> arguments[0] = 2; x is 1)(1) # true
Any developer enabling strict mode should be testing heavily in browsers that actually support the feature. There have been a few high-profile meltdowns already (on BoA, Intel, eBay, etc.) due to devs not understanding the feature, or concatenating a `"use strict"` script (not wrapped in an IIFE) with non-strict code.
JSLint doesn't help matters, as it errors unless `"use strict"` is declared (unless run with the "sloppy" option -- something I'm sure devs love). The absolute worst scenario is for a browser to implement some kind of heuristics-based approach to respect the `"use strict"` prologue; what Brendan Eich calls a "strict quirks mode".
All that said, I'm a big fan of `strict`. It might be a good idea to use it in production, and strip the directives out when deploying.