Worth it at all?
That's like asking what the S&P index will be next year. Nobody knows.
Mining is a form of speculation. A miner is speculating on the two unknowns -- the future exchange rate and the future difficulty level. The profitability can fluctuate but generally reverts to roughly break-even. So most miners who see gains are those who mined and saved their proceeds and then after a run-up sell the coins at a nice profit This really is not much different from speculating on the exchange rate. In fact, those who simply bought coins instead of buying mining hardware end up with more coins at the end than the miners do -- in most circumstances. If you are needing to pay electricity from your mining proceeds, then you won't have many coins left and if there is a rise in the exchange rate you will not really benefit much from that.
Now if the exchange rate drops, miners generally do better than coin speculators on a "per dollar invested" comparison. But then again, that just means miners lost a lower amount (in USD terms) than did speculators of the coin.
But seriously, there are like tens of thousands of GPUs getting taken offline from Bitcoin mining. Many of those will switch to Litecoin -- and since many of those rigs have already been fully paid off thanks to Bitcoin mining revenues, the operators would be happy to mine at a break-even level, or at a loss even with the anticipation that the exchange rate for the alt will rise in value. In other words, if you are investing in hardware you are having to compete with others who essentially see their hardware investment cost as being "zero". So you probably don't want to do anything unless you have some other purpose for the hardware you would be acquiring.
