CPU only is fine, Darkcoin was supposed to be cpu only...but that didnt last long.
Most of the previous "CPU only" coins are really scams and the developers already have GPU miner or know how to write one. There are a very few exceptions, almost certainly including this one.
I don't expect a really dominant GPU miner any time soon, maybe ever. GPUs are just computers though, so it is certainly possible to mine this on a GPU, and there probably will be a some GPU miner, but won't be so much faster as to put small scale CPU miners out of business (probably -- absent some unknown algorithmic flaw).
EVeryone focuses on botnets because it has been so long since regular users were able to effectively mine a coin (due to every coin rapidly going high end GPU and ASIC) that the idea that "users" could vastly outnumber "miners" (botnet or otherwise) isn't even on the radar.
The vision here is a wallet that asks you when you want to install: "Do you want to devote some of you CPU power to help secure the network. You will be eligible to receive free coins as a reward (recommended) [check box]." Get millions of users doing that and it will drive down the value of mining to where neither botnets nor professional/industrial miners will bother, and Satoshi's original vision of a true p2p currency will be realized.
That's what cryptonote wants to accomplish with this whole "egalitarian mining" concept. Whether it succeeds I don't know but we should give it a chance. Those cryptonote guys seem pretty smart. They've probably thought this through better than any of us have.
Yea, and guess what happens when you get free coins in your wallet just by devoting some of your CPU power to help secure the network?? Drastically lower prices of the coin, as everyone and their grandma would have piles of Monero...which is extremely stupid...
Also, darkcoin's darksend is already anonymous, not a matter of if it will be in the future when it already is...The implementation of Ring Signatures and I2P to Darkcoin are just bonuses to it's anonymity, where the masternodes will be used as incentive to uphold the network, and the I2P and Ring Sigs provide the anonymous aspects(the masternodes/darksend would also still provide anonymous transactions).
Essentially, darkcoin has/will have 3 things, Darksend/Masternodes, Ring Signatures, and I2P.....Perfect anonymity, compared to Monero's horrible scaling with Ring Signatures and it's unknown/botnet raped CryptoNight algorithm.