I like "sweep" -- it has very clear semantics that I think users will understand: "Take all the funds that were sent THERE, and send them to me RIGHT NOW."
Automatic sweep-every-once-in-a-while functionality would be fine, as long as it was coded properly (sweeps should only be done if you have the full block-chain, not if you're busy catching up, and shouldn't be done immediately to avoid a flurry of accidental double-spends if you have several wallets setup to sweep the same key(s)).
I don't like "import" -- it has muddy semantics that I think users will not understand. "You kind-of-sort-of own the funds that were sent THERE, unless somebody else happens to have a copy of THERE that you may or may not know about."
Import is bad because it can lead to a situation like:
Start up bitcoin, see you have 1 BTC in your wallet (sent to an imported private key in block 111,000)
So you send half of it to your friend to pay for lunch.
... bitcoin chugs away, and it turns out that 1BTC was spent already, in block 190,000.
User is all "wtf??? where did my BTC go???"
If you're an uber-geek and know what you're doing, then you should use geeky, dangerous tools like PyWallet to do what you want to do.