"Apart from securing Bitcoin, the energy is wasted"
Is there another way to phrase that?
Yea, thats unfairly negative.
"Mining gold takes energy, apart from increasing the supply of gold, most of which will simply be locked away in vaults, the energy is wasted"
"Validating and transporting cash takes energy, apart from discouraging counterfeiting and moving the cash from place to place, the energy is wasted"
People complaining about bitcoin's energy usage are ignoring the externalized (and thus hidden) energy costs in the alternatives. Perhaps bitcoin is worse right now given the low amount of economic activity, but its nowhere near as bad as a simplistic analysis would make it sound.
Ob pedantry: The 21M limit comes not from the quantization limit at 1e-8, it arises as the limit of the geometric series. If the bitcoin precision is increased the total number of bitcoins will not go past that limit.
You're also overstating the current blockchain size. The client keeps orphan forks that it heard about plus a number of excessively bloated indexes. The blocks themselves are in blk0001.dat. On client I bootstrapped a few weeks ago (so it has some amount of dead forks in it already) is 285MBytes.
The blockchain can also be significantly compressed because almost all txn use the same script and because public keys in signed transactions can be reliably derived from the signature. (It's not clear that Satoshi knew this, but even so— it takes a bit more computation to validate without the public key.) Just running a simple compression on it that doesn't take advantage of the ability to recover public keys shrinks the file to 190MBytes.