The scheduling workflow in Google products is all messed. You're constantly switching between email messages and your calendar to see if the suggested time works. It's a huge waste of time. If, like millions of people, you use Gmail to schedule meetings, and Google Calendar to keep track of them, this little interface improvement in Gmail is going to save you a huge amount of time.
Luckily, Google used its data crunching prowess to fix this silly problem. Google will now start parsing your emails for dates and lightly highlight them. If you click on one of those dates, a little dialogue will pop up showing you the day and what else you have going on. If the time works, you can schedule it up -- all without ever taking your eyes of the message.
The update is rolling out to US English users over the next week, with expanded language support on its way. It can't come soon enough. [Google]