"4. Will Nokia Multimedia Transfer transfer iTunes Plus songs (iTunes tracks without digital rights management)?
Yes. Currently iTunes Plus files do not play on existing Nokia products, but are modified during transfer by Nokia Multimedia Transfer so that they do play. The modification process does not affect the audio data, so the original quality of the iTunes Plus songs is preserved (this is different to version 1.0).""
So it's confirmed to be lossless.
"7. Is music artwork transferred?
If you add your own album artwork to an album, it is included with the music files when transferred, but only the latest Nokia products will display this artwork. Artwork that is automatically downloaded from the iTunes Store is not transferred."
And the metadata, including artwork, is preserved, but will only display on the latest Nokia devices - to my knowledge, this would be the current generation of N-series only (eg, N95).
However if you don't have one of those phones and still want to see some metadata I will update Plus Music Fixer (it will require a change to support the .mp4 extension NMT applies, and some detection to make sure it doesn't try to edit videos).