I'm also divided. One side of me says:
- Rename "Generate Coins" to "Help Network" and don't even write about a reward in the pop-up.
- Put a pop-up warning saying that it's better to use a more efficient miner (power-consumption-wise) to help the network if the user has a graphic card.
- Improve miner (at least add SSE2 support, etc.).
I think having this option in the default client is a good thing for the network.
The other side of me says the on-board miner won't ever be as efficient as standalone miners and it will be a waste of resources. Plus, I'm guessing none of the alternative clients does/will have a built-in miner. I still voted for "keep it with a warning" option.
As it is there is such a significant difference between the two. I imagine as 5970 and then 6990 prices fall the gap will be even larger and with increased mining / difficulty CPU mining will be even less efficient. There will be a point when it's beyond pointless to CPU mine. I would guess as it stands now you could spend enough on electricity to buy an ok GPU before you get a block. In 3 or 6 months it will be even worse.