"A major problem that I have with the new interface is that Gmail has gone from text-based buttons to an icon-only design."
The text is there, it's simply been converted into tooltips. Are you really going to need to have the text there after using the button a few dozen times?
"The bad is that the compact is hard to read, and comfortable displays less information than the classic Gmail design."
Perhaps it's because I'm using a custom theme and so my view is different, but I don't really see much different between "compact" and the old design.
"Google has also removed the bottom toolbar from the interface. So if you're at the bottom of your inbox, you have to move the mouse back up to the top of the screen to archive, spam, mark messages read, and so forth."
Seriously? Are you going to suffer from RSI from moving your mouse up the screen each time you view your inbox? Not sure why your cursor keeps ending up at the bottom of the screen each time you finish checking your inbox.
The only points I can really agree with the author on is that the new interface is slower to use than before, and also on the excessive use of whitespace -- there does seem to be a lot of unused area with the new look (although it does make my theme look prettier).