We're talking KH/s. Just from my own experience:

Intel Core i3 @ 3.2GHz gets me around 28 kH/s
AMD A8 5600K @ 3.6GHz (technically it's an APU, not a CPU) gets around 36 to 38 kH/s.

As you can see, it's not a lot, but there are more powerful CPUs available. CPU mining is only profitable for alt-coins, and even then, you'd most likely be better off with a GPU.

I still mine some alt-coins with CPUs because I already I have the CPUs, but I wouldn't buy a CPU just for this.

As someone else said, you can use GPUs for scrypt mining, but you can also use CPUs with cpuminer.

My "blocks" folder is currently at 11GB. Since block size is limited, the growth can only be linear in time (even if we occasionally increase the block size limit), but storage per dollar increases exponentially over time. Therefore, I don't see it as a problem in the long run. Also, see http://blockchain.info/charts/blocks-size

Bandwidth is currently a tougher question. I typically see bitcoin-qt using tens of kB/s, sometimes running at 200-300 kB/s for minutes or hours (this is mostly my upload to new users downloading old blocks). Unfortunately, I don't have any solid data to offer, just these observations.