@Jack - on the energy usage side, modern ASICs and whatnot appear to be extremely energy efficient, although some alts can be mined with CPU/GPU, any serious miner uses specialised equipment. It's an interesting question though - if hypothetically crytpo ever replaced fiat (can't see it happening myself), how would the energy costs of maintaining it compare to the energy costs of running a huge note / coin minting operation? But yes, either way energy usage (especially on the massive farms China are said to have, though I'm sure they're not the only ones) is a very big concern either way.
Re: inflation - whilst Bitcoin and others seem to naturally work against too much inflation with halving and increasing difficulty of hashing, there are also several POS (Proof Of Stake) coins whose interest rates cause them to run on massive hyper-inflation - then again this is self-limiting as eventually these coins (for instance SPROUTS) lose all value and eventually cannot be traded even for one satoshi (0.00000001BTC, the [currently] smallest unit of Bitcoin exchange)