One of the disconcerting things about Web applications is that they can change in small ways underneath your very feet. This morning, I checked mail in Gmail and saw that I needed to edit an article for Doug, but when I came back to reply to his message, I noticed that the Gmail toolbar had changed, both in style and contents. Luckily, Google's engineers posted on the Gmail Blog to explain the changes (which may not be available for all users for a day or so - Google rolls changes out in waves, which is another disconcerting aspect of how Web applications update).
Stylistically, the buttons became large and more rectangular, and Google also added a pair of menus: Move To and Labels. On first glance, the menus seem redundant, since they both contain all the labels you've created. (I must admit, I had a brief moment of glee seeing Gmail's interface designers come up with something that's at least visually similar to Eudora's Mailbox and Transfer menus.)
Here's the trick. Gmail doesn't really do folders, as we think of them. Instead, it offers labels, which are in many ways more powerful and flexible, since you can apply multiple labels to any given message. For instance, you could have a label for messages to or from your closest colleague along with a label for a particular project you're both working on, and any given message could have one or both of those labels.
But if you're used to folders, it can take a little time to understand how labels can be most effectively used (and to be honest, I'm still largely using labels as though they were folders). People who are new to Gmail often find the labels confusing, and have trouble mapping between folders and labels. Further confusing the issue is how Gmail implements IMAP, where labels do become folders in your email client.
So the point of the Move To menu, much like Eudora's Transfer menu, is to apply the selected label and then archive the message, which essentially removes the Inbox label. Archived messages appear in the All Mail collection in Gmail, and if any other labels are attached, they'll appear in those collections as well. In other words, users accustomed to putting messages in folders will probably find the Move To menu a familiar way of filing messages away.
Although the Labels menu appears similar to Move To, selecting an item from it merely applies the selected label to the current message or selected messages. Checkboxes make it possible to apply multiple labels quickly. Previously, the labels were accessible only at the bottom of the More Actions menu, but given the dominance of labels within the Gmail interface, it makes sense to promote them to a top-level control.
In my ongoing real-world test of Gmail via its Web interface, I'm doing pretty well. The main commands that I find myself missing from Eudora are Send Again (to resend a sent message) and Redirect. Send Again hasn't been a major loss, since it's easy enough to copy and paste text from a previously sent message, or to use Forward and tweak the headers. But I do bemoan the loss of Redirect, which enables forwarding of any given message to any arbitrary address in such a way that it appears to the new recipient that it came from the original sender. Not having Redirect is frustrating, but not a deal-breaker.