It did take me 12 hours to download all the blocks though. Isn't this going to become a huge issue for new users a couple of years from now when it takes days to download all the blocks? What if BTC is still around 100 years from now? How long will it take then?
There are other option available in the future. Including, but not limited to, simply including a recent copy of the blockchain in each new client release to be downloaded directly rather than over the p2p network and verified by each client upon first start. It's the verification process that takes most of the time, not the actual downloading.
Does that not introduce centralization?
Not really, because at this point the client will still verify all the blocks upon first start, regardless of where the blockchain came from. In the future, there are likely to be clients that come with a blockchain already in it and trust this included blockchain, but that would require trust in the client developers.
In the future, only a few pool owners, heavy miners, and people with a high number of bitcoins will actually store the blockchain, because it will reach into the TB's of size quite quickly. Most other users will connect to one or more of these blockchain holders to verify account balances using a lite client (chainless client).
At least, this is what I see happening if there is wider acceptance and use of bitcoins.
This needs to happen within 1 year given current transaction rates. Blocks have increased in size now that real transactions are being done and a small fraction of blocks (the new blocks) are taking up increasingly larger percentages of the total block size. Unless bitcoin is deserted, in 1 year it will take over 1 GB to download all of the blocks. No new users will participate if it takes 1 GB download just to start.
The clock is ticking and what you describe needs to happen now.