I found Joan Fontaine's voice acting to be somewhat surprising because it felt less timid then her onscreen version. Maybe she could have taken the role in a different direction if she had the opportunity in the film. I liked her better in this, even though there isn't too much to base that decision on. She seemed more confident in what I heard. Frederic March is actually a favorite actor of mine, so I might be a little biased in thinking he did an excellent job as Rochester for the little he had to say. At least he seemed more invested in the character than some other drier, more mundane readings of the role.
The adaptation mostly had Jane narrating events, with Rochester interjecting lines. There were no other characters voiced. One scene that I thought was fun, was how when Jane was leaving the party, Rochester pointedly went after her, and called her back to have a little tête-à-tête. In the ending however, instead of Jane leaving Rochester to go to the Rivers, or some unnamed far away area, Jane says she goes to Ferndean where her Aunt lives - an Aunt who didn't like her much when she was young, but was happy to see her now. Oookay. Obviously the Lowood/Rivers sections weren't adapted for this. The reunion was sweet though, and overall I actually enjoyed this extremely shortened version of the story.