I thought transient-mark-mode was enabled by default in recent releases?
Correct.
ido doesn't become really amazing until you add ido-ubiquitous (which makes most minibuffer completions use the ido interface, as opposed to just file opens) and flx-ido (which allows fuzzy matching).
Yes, I've found using ido that way together with gtags to be particularly slick.
It is enabled by default. I've updated the list to indicate that transient-mark-mode and blink-cursor-mode are on by default in modern Emacsen and that uniquify will be enabled by default in 24.4.