If SLC has figured out, how prune this massive "transaction list", we better copy this or BTC/LTC become useless faster, than any of us wants to imagine.
It's already been implemented in some of the Bitcoin clients.
This is not the same thing as a lite client. It is using an account ledger instead of a transaction ledger. It is a completely different system, and one that, imo, makes a lot more sense. Although from what I can tell they are doing a piss-poor job of implementing it and removing a lot of the features of bitcoin. RS claims to have "just thought it up" but there are a good 10 or so threads on bitcointalk about it, including the various proposals I've made for encoin. Probably the original thread:
https://bitcointalk.org/index.php?topic=505.0