Read About Gmail, including screenshots and a FAQ. There is also Known Bugs list with solutions to various problems people have reported.
Here is what irks me about it.
As of 2004-10-06:
Labels should be applicable to individual messages, not threads. They should also be dynamic. So I can have a "label" called "from bob" and clicking on it should reveal all messages specified by the criteria in "from bob". An easy way to implement this would be to "save" search queries and re-search using that query whenever I click on "from bob".
I just sent this to the Gmail team. Maybe they'll implement it:
I want to save searches. So that I can issue a search query like "from:bob subject:important" and save the query (not the result set) as "important from bob". Then I can periodically click on "important from bob" to see what important things bob has recently sent me.
This should also work retroactively to messages that have been stored before defining "important from bob", and redefining "important from bob" should work as expected.
In addition, I'd like to specify dates in an easier way, like "date:2004-08" as opposed to defining exclusive boundaries "after:2004-07-30 before:2004-09-01" which is hard to think about. Then I could define searches like "sent in august" and "sent in septemer" or "sent in summer" or things which make sense to me.
As of 2004-08-29:
Composing messages is not done in a monospace font. I want to at least have the option to use a fixed width font to write my mail.
Displaying messages cannot be done in a monospace font. I want to correctly see messages that have, for examples, indented code.
Conversations are a nice way of saying threads. Traditionally, threads have been hierarchical. Gmail flattens them. When I receive a message and forward it, replies to the forward are attached to the original message. When I reply to the original message, both "conversations" are flattened and confusing to follow.
Conversations are good for the most part, but I'd like to break individual messages away from the bonds that Gmail imposes.
Searching should operate on individual messages in addition to conversations.
Searching should let me find partial words (find "houses" when searching for "house", for example.)
Reply-to headers should be optional. All my messages now include a reply-to entry that confuses mailling list users.
Other than these deficiencies, Gmail is a fine tool.
http://michal.guerquin.com/gmail.html, updated 2004-10-06 11:52 EDT