My take on GMail.
Ok, I've only been using it for a short while, but I haven't quite gotten the hang of it yet. The first issue is that all email is sorted by "conversations", which is basically what everyone but Microsoft and GMail call threads. For those of you that don't know what that means, a thread/conversation is just what it sounds like, a collection of email messages relating to a specific topic. On the most basic level, a conversation is an original message and any replies to that message. Certain mail clients assign a thread ID and thus you can change the message subject and it will still be a part of the original thread/conversation. Either GMail or Yahoo doesn't support thread ID because I changed the subject on a thread and GMail started a new "conversation".
There are a ton of keyboard shortcuts, which is interesting for a webmail client. Seeing as I used pine for my email for 6 years, I'm quite used to navigating my email with a keyboard... in pine! Using it in gmail isn't as easy as I expected. There are keyboard shortcuts for navigating various messages and conversations, but very basic actions, like cancelling the composition of a message, has to be done by mouse. I do love that the keyboard shortcut for reporting spam is the excalamation key... it just goes so well with most spam: "Ge.t a m.a$siv3 mem.b3r! buttercup obtuse bingo cxoiuqweijfd4klhjd7" My natural response is "!".
GMail has a concept of "All mail" and "archive". The main action for all emails is to "archive" it. It doesn't place the message in the trash, it doesn't move it to a specific folder, it just moves the email out of your inbox. The only way to view archived mails is to use the All Mail view. All Mail shows any mail in your inbox, your sent mail "folder" and anything you have archived. It does not show any spam or trash emails.
Instead of supporting folders like most email clients (web or desktop), GMail has introduced the concept of "Labels". Well, I shouldn't say introduced, but this is the first time I've seen it in relation to an email client. Instead of storing a conversation (see above) in various default or unique folders, you can assign one or more labels to the conversation. Let's say that you wanted to save all conversations from a specific person in a specific folder and you wanted to save all conversations about a specific topic in a specific folder, what happens if your specifics collide? Do you try to decide which folder takes presidence? With labels, you can give the conversation labels for both the sender and the topic. Like most folder views, there is a list of labels so you can jump to the list of all conversations with a specific label.
GMail also supports filters which works hand in hand with labels. You can filter on sender, receiver, subject, words in the body and words missing from the body. The actions you can take are skip inbox (meaning it places the mail into the archive (see above)), apply a specific label or move it directly to the trash. You cannot mark anything as spam through the filter.
One little feature that I saw in their help files but they did not actually implement related to attachments. Instead of showing the common and generic paper clip icon to denote an attachment, GMail would use an icon to represent the file type of the attachment. If it was a PDF, the common PDF icon would be used, etc. I tested this out, and it's just a paper clip. Shucky darn.
Overall, I'm sure that I will get used to conversation view, labels and archive and be very happy with my free 1000 MB webmail client harnessing Google!