New version is out. It mainly adds a tuning parameter called -sievesize. Use it like this: primecoind -sievesize=2000000
I did some experiments with the sieve size and I was able to get significantly higher more blocks with a sieve size of 2M on a Core i7-4770k. There did seem to be some variance though.
The parameter will also affect your primespersec but it's always better to measure the block rate for now.
"Use it like this: primecoind -sievesize=2000000" <--- where exactly do I use this? Tried to type it in the console and got an error message.