It's all around inefficient.
My grip list:
1.) The interface sucks, while the ribbon in MS office (and every other program that uses it) is implemented correctly the one in Creo blows. The drafting ribbons are the worst.
2.) WTF is the purpose of the activate button? NO software requires you to activate the window after you click on it, that's in the action of switching windows. This is an outdated feature and shows PTC's unwillingness to move on.
3.) When closing a window you're never asked to save, but Creo still stores the file in session. When I close the part and it's not opened in an assembly get rid of it, in this day an age I see little to no benefit to keeping an unopened part in memory.
4.) Drawing mode makes me want to punch a baby. The interface is terrible it has always been terrible when you take crap and put a ribbon on it, it is still crap...but with a pretty ribbon.
5.) Assembly mode sucks, it's much better than ProE but still sucks.
6.) The Esc key is not consistent, when I press it I want to "escape" out of the damn function I'm in. I can't even say this works half the time.
7.) Collection windows don't collect automatically, what's the point of the collection window if I still have to hold down Ctrl key?
8.) The mirror command often fails after an update and regen. (at least for me, I have to delete the mirror and do it again).
9.) If the feature in the part fails to regen I see that, I don't need an inescapable info window telling me on the opposite side of the screen.
10.) Draft function is lacking, I often have to leave all the drafts out and let my supplier add them.
11.) I don't understand why there is still history based modelling in an assembly model. Load the parts, and then the constraints... oh wait it's so you can keep selling Mechanism isnt' it?
12.) No reload from source file button. (if this exists I have no idea where it is) instead I have suppress the file everywhere it's used, clear session memory, delete from workspace and then reopen the part and regen.
13.) Working directories are locked, this is the 21st people I think we can do better than this.
14.) I hate the layers interface, I just hate it, it's clunky and I have to click a lot also they are becoming an obsolete feature.
15.) Why is the accept button the middle mouse wheel button? I loath this feature, especially in assembly mode.
16.) The show/hide datums is terrible. Why do I have to create a datum in the model just to use it in the drawing?
17.) No 3D sketches, this is a 3D modeling program and I can't make a sketch in 3D? Instead I have to use a series of sketches, projected curves and datum curves to create something rather simple in other CAD programs.
18.) The piping interface needs improvement...lots of improvement. The workflow is so batty I avoid using it.
19.) While in "Insert" mode and you resume the last feature it doesn't resume the previous features. (an action outside the insert should automatically cancel insert mode.)
20.) I hate the sketcher, the interface is clunky and doesn't by default lock a dimension when you set it.
21.) Still no mouse gestures in modeling or sketcher. Instead I have to looooong right click (stupid) and select what looks like a checkbox for a line/circle wtf was the thought processes on this?
22.) Why the hell do I have to long right click something? I just don't see the purpose since the short right-click does nothing.
23.) When creating a new sketch and you have a plane selected, Creo generally assumes wrong 98% of the time. Just pull to the nearest normal to view.
24.) While inside a sketch you can't hide/unhide features.
25.) The "undo" button is nothing more than false hope. If you're going to have it make it more useful than what it is. See gripe 12
26.) Copy/Paste feature is lame, I can't preview my sketch plane before I place the internal sketch.
27.) While in assembly mode you can't easily hide a part or change/remove cross-sections.
28.) No box selection or lasso selection tool. I know there is something like this in the sketcher, but it would be nice to have this everywhere.
29.) No multi-monitor support, I have three monitors but Creo can only work in one at a time.
30.) The help key doesn't pull up help to the function I'm working in by default.
31.) No option that I can see to create a drawing from the file... instead I have to click new-->drawing-->template and enter the part number in the file name box...again (not efficient)
32.) The sheetmetal tools are clunky at best, and when you do a "Save As" it doesn't change the family table name to the new file.
33.) No keyboard shortcuts for views. Instead I have to use mapkeys so it's really not a shortcut.
34.) Maybe it's just me, but I'm not a fan of how Creo loads assemblies. It should load all the parts first and then apply the constraints in my opinion. See gripe 11.
35.) While in sketcher, there is no way to dissove a point to make two line sigments one.
36.) When you have a sheetmetal part and you do a "Save A Copy" and rename the part, the family table doesn't change and the drawing doesn't refrence the new part number.
37.) It is unclear whether you select the feature in the model tree or in the 3D view on some tools, ex in Pipe info you have to select the segment in the view not the model tree.
38.) This error: Group member feature must be younger than group head feature. By far one of the dumbest errors I've come across. I despise using groups for this stupid issue. See gripe 11 and 34
39.) I have to click a 10-25 times to select something WHY?!
40.) When a feature fails I get the info box, but what the is the point of an "Ok/Cancel" confirmation box after I click Ok or Cancel in the info box? Seriously the person that thought that should be kicked in the balls.
41.) Failures have no description of the failure, it never tells you what exactly is causing the failure.