As other reviewers have pointed out, the biggest changes to Office 2013 from Office 2010 are SkyDrive integration, touch gestures, and a flatter UI to match Windows 8. Since I don't use SkyDrive often, don't have a touchscreen, and am indifferent to the flatter look, I'll leave those aspects to other reviews. If you're like me and aren't particularly excited by SkyDrive (which still isn't as versatile as Google Docs for real-time collaboration), then Office 2013 is practically the same as Office 2010 in terms of how everything works - most of the time. This is not a bad thing, at least in my opinion, since I really liked Office 2010 and its improved Ribbon UI.
What I wanted to talk about here are the changes that Microsoft has made to Office 2013 from Office 2010 that I've noticed, changes that might impact daily workflow for users upgrading from previous Office versions.
OneNote 2013:
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I spend at least 4 hours a day in this program, so I'll start with this. As far as I can tell, there are no significant changes in terms of features. Buttons on the ribbon are shuffled around a bit, but the feature set is still the same, as is the file container (*.one) and notebook type ("OneNote 2010-2013").
However, there are 5 new issues that annoy me every single day.
(1) Full screen and pinning the ribbon. In 2013, going into full screen mode means that everything is hidden, except for a very short horizontal bar across the top of the screen. To access anything on the ribbon, I have to click on this bar to show the ribbon first. If I want to pin the ribbon so that tabs are visible at all times in full screen mode, I have to click on this bar, click a menu button near the minimize button (also hidden in full screen), and then click Show Tabs. However, OneNote does not remember this setting. Thus, every time I exit full screen mode or restart OneNote and then reenter full screen mode, I have to re-pin the ribbon again. On an ultrabook, I want more space for taking notes, but I also use the ribbon extensively and would prefer to have it available. This problem did not exist in OneNote 2010, which remembers the user's full-screen ribbon settings.
(2) Inserting multi-page printouts. The new default behavior in OneNote 2013 is to place each page of the printout on a separate "page" of the notebook. I prefer to put one entire lecture on each "notebook page", regardless of how many pages or slides the professor gives us. I've also never come across anyone who prefers to have only one printout page on each notebook page. So for instance, if I were inserting a 30-slide Powerpoint, OneNote 2013 would create 30 new notebook pages. There is an option to turn this off in the options, but OneNote then shows a dialog box asking me to choose between the two options every time I want to insert a printout. Since I insert several files a day, this gets annoying very quickly. Once again, OneNote 2010 did not have this problem.
(3) Inserting more than 1 multi-page printout on the same notebook page. If I try this, then the second printout is somehow inserted under the first printout, i.e. the first printout overlaps and covers up the second printout. It only happens when the printouts are both at least several pages long or if I've annotated the page already; the program disregards my cursor location. To work around this, I have to put the second printout on a new notebook page and then copy/paste the printout pages back to the first notebook page. This problem also did not exist in OneNote 2010.
(4) Zoom level changes when inserting printout: it always defaults back to 100%. I take notes at 115% on my ultrabook, so every time I insert a printout, I have to readjust the zoom level.
(5) Drawing tools. I have no idea how Microsoft managed to mess this up when going from 2010 to 2013, but half the time I try to draw an arrow, it ends up being a line with a V in the middle, or the arrowhead is completely detached from the line. In fact, I can't even draw a plain line properly sometimes. I haven't tried the other shapes much, but I wouldn't be surprised if there were problems there too. I've given up and resorted to drawing arrows freehand with the pen tool instead.
These issues may seem minor to some, but they affect me every day, so I wanted to give a heads-up to anyone else who uses OneNote the same way I do. I wish that Microsoft had spent more time implementing useful features (e.g. still can't rotate or crop a printout; search results are still clunky) or at least providing options to change these new behaviors in settings.