Digicoin: I'm going to wait a bit more because I'm trying to find a range proof more efficient than Schoenmaker's bit-by-bit proof. Also, I would like to see if I could introduce multi-input transactions (as proposed in Adam's "Ringcoin" homomorphic scheme) into this scheme.

Adam: The url is working fine in my browser but I will change it.
I need it to be decryptable because you don't know if the sender of the transaction will send the right value and random value. In your homomorphic scheme this isn't a problem because you could simply ignore the transaction but this scheme runs on top of the mini-blockchain which actually has accounts. Suppose you have an account with balance x and corresponding Pedersen commitment xG+vH. Then I send you a transaction with value y (it can even be zero) and random value r,so yG+rH, but I send to you encrypted any other values (let's say y' and r'). The two commitments will be added and your balance will be (x+y)G+(v+r)H. Now you can't open the commitment of your own balance so, you can't make transactions because you won't be able to produce the required ZK proofs. Finally I can send a message telling you to pay me z bitcoins or I won't tell you the real values.
Also, the mini-blockchain only stores transactions for a limited time (in cryptonite's case it's 7 days) so if someone receives a transaction and doesn't connect to the network in 7 days, he won't see the transaction and will no longer know its own balance.