Any truth to it? If so, that sounds serious enough, and a direct consequence of Google's conscious choice to reinvent the IMAP wheel.
(apologies if it's already been posted – blogocoped/search returns nil on "IMAP" keyword, and I don't see it in the forum in the past few days....)

http://weblog.timaltman.com/archive/2008/02/24/gmails-buggy-imap-implementation

"As Opera Software's lead QA for Opera Mail, I get a lot of opportunities to analyze the communication between IMAP clients and servers. Gmail is by far the quirkiest and most troublesome IMAP implementation I've seen to date. Gmail's own documentation describes how clients must work around the deficiencies built into their implementation. I understand that Gmail's IMAP implementation is still in beta (a Google norm), but some of the basic design choices are at the heart of the problem, which leads me to believe they won't be changing. These decisions are anti-IMAP (even the IMAP spec. author finds Gmail's IMAP disappointing) and cause Opera users headaches. [...] "