"2. Mailbox size is not an optional column or filter field in the console now, so we cann't add this column or sort the mailboxes by size in the console. Part of the reason is that mailbox size is one property horned by Store (returned by Get-MailboxStatistics), to retrieve this property along with other mailbox properties horned by AD (returned by Get-Mailbox) we need to access Store in addition to accessing AD, this could be a perf issue, expecially in case of a huge amount of mailboxes. "
Having to figure out cryptic command-line statements to do what should be a simple GUI function IS a performance issue. Give me the column and let me use it or not use it depending on MY assessment, don't be patronizing and make the decision for me. I am regretting transitioning from 2003 to 2007 because of the crippled GUI.