In upgrading from 4.1 to 4.2, we notice that customfields are -not- saved when previewing. Enter customfields data, click preview and they are not saved (with either a new entry, or populating CF for the first time in an existing entry). If the entry is saved first and then previewed, it works as it did previously.
Reported on Movable Type 4.2
I'm noticing something that may be related: when a custom image asset is added to a post it doesn't appear to be saved properly. For older posts the image is shown next to the upload button in the entry screen and displays properly in the post; for new posts I just get a "View Image" link next to the upload button in the entry screen and the image doesn't display in the post.