It's been a long, slow decline, but outside of a major jump in cryptocurrency prices we have finally reached the end of the road for GPU mining. That's not to say that people won't continue to mine with GPUs, but based on the cost of electricity and the current price of Bitcoin combined with the alt-coin exchange rates...well, you get the point. GPU mining is "dead". Let's quickly run some figures to give you an idea of where we stand.
The best-case mining opportunity right now (as far as I can tell -- there are so many coins that it's possible I'm missing some "secret" coin that's highly profitable) would be GPU mining of Monero, one of the Cryptonight coins. With the current difficulty, block reward, exchange rate, and price of BTC, a rig with three R9 280X GPUs might mine around 1.5 XMR per day, which would equal about $1.90. That same rig will draw about 450W of power, and at $0.10 per kWh you'd spend $1.08 per day in electricity. Factor in wear and tear on the GPUs and the net profits of $0.80 per day probably isn't worth your time, but that's about the best option for GPUs right now.
Okay, that's XMR and Cryptonight, but what about some of the other proof of work algorithms that can't be run on an ASIC? We have X11, X13, X15, Keccak, and maybe a few others as potential PoW options. There are a few others as well, but let's just stick with those for now.
X11 was made famous with Darkcoin, which is currently averaging a difficulty of around 3300 with a block reward of 4 DRK being typical. If your hash rate is 12000 KH/s for X11 (which is about right for three 280X GPUs), and your power draw is only 450W, you'd still be in the red. You might mine 0.3 DRK per day, worth about $0.90, with a power cost of $1.08. Even R9 290X wouldn't be much better: 16 MH/s for three 290X GPUs and at a power use of 500W you'd basically break even. CANN is about the same right now, so is URO, and basically we're looking at best-case breaking even or making pennies per day per GPU.
Actually, your best bet is often to just go with leasing your hash rates on a service like NiceHash -- let others do the work of figuring out which new alt-coins to mine, let them take the risk, and you just get paid directly in BTC. Or go with a multi-pool like BlackcoinPool, MultiPool, WafflePool, etc. The current best rates for X11 are around 0.0003 BTC per MH per day, so three R9 290X could make about $1.90 per day, with a power cost of $1.25 (give or take). That's "profitable", but not enough that I'd seriously invest time and effort into it. So X11 is out, unless prices go up, difficulty goes down, or hash rates can be increased without using more power.
X13 and X15 really aren't much different in concept from X11, just with lower hash rates thanks to the additional hashing algorithms. X13 you might make a bit more per MH (currently looking like 0.00037 BTC/MH/day, give or take), but with lower hash rates in general it's less profitable (or more unprofitable). X15 is paying less than X11 and X13 with even lower hash rates, so obviously that's out as well.
If you're after really high hash rates, you could look to Keccak, but just because it has high hash rates (450MH for a 290X?) doesn't mean it's profitable. The going rate is about 0.0000023 BTC/MH/Day, or $1.25 per day for 3x290X. Nist5 is another "faster" hashing PoW, but it's only about three times the hash rate of X11 and it's paying about 10% of X11, so that's a dead end as well.
The net result is that across the current list of coins and PoW algorithms, there's really nothing out there that can even hit a 2:1 ratio for value vs. power. The best I can currently find is Monero, which gives about a 1.7:1 ratio of income vs. electricity. If you were to use a $300 R9 280X GPU, not accounting for the rest of the PC, you would need to mine Monero for over two years straight just to break even. And let me tell you, my personal experience is that running a GPU 24/7 at 100% load (which is what you do with cryptocurrencies) could very well kill the GPU before two years pass -- or at least the GPU fans will likely need to be replaced.
If you're wondering why I've become so pro-ASIC (or pro-Hashlet), this is the answer. All of my GPUs are now powered down, and I for one welcome the blessed silence. Maybe I'll fire them back up to help heat my house as it gets colder, or maybe prices will shoot up again and make GPU mining profitable. Until one of those things happen -- or something else comes along to make me want to mine with GPUs -- I'm going to be investing my time and energy elsewhere. Anyone interested in buying some GPUs?