I've been doing almost exclusively JavaScript/Canvas work for over 3 years now and I think it's great, even if it isn't the most technically mature language I've used at length.
I am in a love affair with the weird little language that is JavaScript. I also think it is by far the best language to teach basic programming (and because of that I think JavaScript is hugely important in its own right[1]).
The amount of time it takes to whip up a five-cent program with JavaScript without even leaving my browser, heck without even leaving this tab is just astounding to me even after all these years.
One thing I noticed in my (not-very-long) career is that more than the language itself, or the "kind of work" as you put it when considering front end vs back end, is not the end-all of importance in determining the enjoyment of my work.
The tools that I use while building things in a language are what really make the work a pleasure. If I wasn't using Chrome's web developer tools I'd probably consider JavaScript to be a nightmarish corpse of a language that punishes the slightest of typos with a silent malicious grin, as code execution carries on as if A.blah = 5 and A.blsh = 5 were both equally worthy of existing to the JS compiler/interpreter. Only by the grace of tools is JavaScript tame at all. Services like BrowserStack[2] help a lot in this field too, as does StackOverflow (helps all fields and needs no introduction, though the StackOverflow JS chatroom is one of the liveliest rooms, and deserves a mention)
With the clarity of the tools for modern front-end dev, I think it's an incredibly enjoyable environment. Certainly the most pleasing one I've found.
[1] http://simonsarris.com/blog/696-the-importance-of-geocities
[2] http://www.browserstack.com/