Is there a way to import my wallet from Bitcoin.org's client into the much lighter Multibit or Electrum? The disk space & bandwidth consumption (not exactly well presented to a beginner) quickly made it unfeasible on home computers.
Not technically the answer to this question but a much more ideal solution for me was to switch over to an online wallet keeper altogether like at http://blockchain.info
Though I've known about online wallets for a while (though not soon enough whence I still struggled to keep bitcoin "clients" being useful and playing nice with their host PCs, thinking it was the only way to control my BTC when I was new) it wasn't until recently that I figured out how to use their Import wallet feature and apply the buried old wallet.dat files, which for me wasn't trivial:
However to get that Python code to finally operate without cryptic errors on a fresh Ubuntu 11.10 Linux required some extra research and package dependencies troubleshooting.
Now, thankfully, bitpennies that continue to arrive at my original BTC address (from the now purged software clients) eventually make it to my online wallet hosting a few BTC addresses, whose funds I could freely transact from there if I want to. No manual transferring from my old address, good.
Last I updated and tried launching again one of those clients it stalled and absolutely PEGGED the network trying to finish its per-design 2-3GB blockchain download before allowing me to do anything (else on the PC, let alone transactions) which didn't seem to be advancing anyway no matter how long I let it eat my PC or how many times I restarted. Where of course that much disk space couldn't be spared, nor shared bandwidth, nor CPU & memory resources it took that PC. 3GB win7 AMDx64, mind you.