Last year I spent a week mining 8 or so litecoins. Today I checked and they are worth close to $11 each, so I turned on my miner and found that currently I'd probably make one coin every hundred days, rather than the one every other day I was making when I was mining last year. It also rose in value - last year my 8 coins were worth much less than a dollar total, so it's a 100x increase since I've mined them.
Seems like a lot of people have joined the bandwagon.
There are a lot of newer crypto-currencies (doge coin being the funniest, but it actually has value) coming along, easy to mine, and going up in value.
It's probably worth mining a few dozen to few hundred of the easier coins, then sitting on them. If they don't gain in value, nothing lost but a bit of electricity. If they do gain in value, it'll be faster than inflation, and a year or two down the road they'll be worth vastly more than what you paid in electricity.
So while you probably don't want to spend time on the popular coins, you might consider spending time on the less popular new coins, speculatively.
For those curious, I use
https://www.coinotron.com/ for my mining. It simplifies things, even though there's some overhead. You essentially work with others in a pool, and get a cut of the "winnings" when you collectively calculate a hash successfully. They hold onto your coins, so you'll have to drag them out and put them into a wallet of your own if you want to maintain control - like mtgox there's always the possibility the site will go down, or someone will break in and steal your coins.
But I started with them, they're still around, and supposedly they haven't lost my coins yet, so I'll stick with them, since other pools and exchanges have come and gone in that time.
I stopped only because my video card I'm using for mining seems a bit flaky in this system, and I had to check on the computer a few times a day to make sure it was still running. I'll let it run overnight and see if my speed goes up after I stop using the computer, maybe round off my litcoins to 9, then I'll try mining some of the other coins and build up small stashes of them. You never know. I won't become rich, but it's amusing all the same.