Version:           3.5.9 (using 3.5.10, Debian Package 4:3.5.10.dfsg.1-0lenny1 (lenny/sid))
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.26-1-686

[As the bug reporting tool might squash the layout of the following: Originally it has been three lists in MediaWiki syntax.]

Current order of the input/modificatable items in the enter new appointment dialog are (top-down, left-to-right):
* title
* location
* category [select]
* date/time
** start: date/time/all day/access
** end: date/time/show as
** repetition
** reminder
* unnamed box for notes
* attachments/+ cross/x cross
* templates
* ok/apply/cancel

However, the Tab key order is as follows, not matching the above order:
* title
* location
* date/time->start/date
** start/time
** end/date
** end/time
** start/all day
** reminder
** end/show as
* unnamed box for notes
[you got lost here, since the focus is totally out of where you look at]
* category [select]
** date/time->start/access
** repetition
* [** unknown, no focus to be seen **]
* attachments/+ cross
* first dialog tab
* templates
* ok/apply/cancel
* and back to title

I suggest to have it in a somewhat more natural order:
* first the essentials for setting up the appointment
** title + location
** category
** start date and time
** start/all day
** end date and time
* second, utility that helps to keep that appointment
** reminder + repetition [layout: put reminder first, i.e. above repetition]
* third, whether and what others may see of the appointment, additional data others might need to know about the appointment [layout: separate this from all the beforementioned ones, put it underneath of them, i.e. in a separate box]
** access and show as
** notes and attachments [layout: add a label to notes]
* ok/apply/cancel

I'd put the templates button next to the title, as if the user intends to make use of a template they mostly need the title and little else but what the template is about to fill in.