Newb here:
There's a question that hasn't been answered, afaik: to what extent are BIP16 or BIP17 backward compatibile?
If I have some savings in a paper wallet, will I be able to spend them after the change?
BIP16 and BIP17 don't invalidate existing bitcoins. If you have savings in a wallet, paper or not, you will absolutely be able to spend them.
After the change, can I opt out of having to use multiple private key confirmations? Can I use my present wallet on 0.5.2 unhindered?
Can I receive btc from a bip16/17 client on my 0.5.2 client?
Absolutely you can choose not to use multiple private keys. I would think it's something you have to opt in to.
You should be able to use your present wallet but would probably be required to upgrade your client.
Frankly, I think the proposed way of doing things is potentially more trouble than it is worth. With a bit of computer literacy, the present client is plenty secure and reliable.
Thoughts?
I don't think computer literacy is quite the right term - to me, this means familiarity with e-mail and surfing the web, using a word processor and a spreadsheet. I consider myself a computer expert, and of course I can make do with the current client. I am sure you are referring to the ability to keep one's computer secure, not just use a spreadsheet, so I'll assume you mean expert.
The problem is that computer expertise is a very high prerequisite to use a currency, and even computer experts get malware and hacked all the time, often without even knowing it. I think it is a foregone conclusion that we need multisig to counter this.