I calculated (figuring difficulty) that it was worth getting the several months of good dividends at the price I bought the shares at. Honestly, I think we have several good months left on this. You can do the math yourself for the current price (BTC0.00365, I think)...
According to profile on bitfunder...
D is the current difficulty
H is your hash rate in Mhash/s = 1 MH
B is the current block reward in BTC = 25 btc
(H*B/D) * (60*60*24 * 65535 * 10^6 / 2^48)
(1*25/26162875.68257) * (60*60*24 * 65535 * 10000000 / 281474976710656)
According to profile on bitfunder...
D is the current difficulty
H is your hash rate in Mhash/s = 1 MH
B is the current block reward in BTC = 25 btc
(H*B/D) * (60*60*24 * 65535 * 10^6 / 2^48)
(1*25/26162875.68257) * (60*60*24 * 65535 * 10000000 / 281474976710656)
When diff rises 20%, you'll not only get divs of (1*25/(26162875.68257*1.2)) * (60*60*24 * 65535 * 10^6 / 2^48) = ฿0.00001602, but the price per share will devalue as much. So, you lose two times: on the dividends and on the share price.
At the current share price it would be 192 days for break even on dividends, considering no difficulty increases. Realistically it won't break even at the current share price. Personally, I wouldn't buy at any higher than ฿0.001.
Like coco23 suggested, you can use a profits calculator with adjustments for difficulty, http://www.coinish.com/calc/# (press the Expert button).
