Initially they aren't apparent, but as you continue working on a larger game with construct, there are some major speed issues. I realize a lot of these probably can't be resolved in construct one, maybe for construct two they can be fixed.
Opening large event sheets - one of my event sheets has about 3500 events, and it takes about 2 minutes to open the first time it's opened. It's faster subsequent times when I switch back to the layout editor then go back to the events, but regardless still takes a while.
Solution idea: even if the initial loading can't be sped up, after the event sheet is loaded, switching back and forth via the tabs from one event sheet to another is instant. Perhaps if the event sheet was kept "open" in its own window the same way other layouts are kept open in other windows, then it would remain plenty fast to switch between a layout and its events.
Previewing games with large event sheets - my game takes over a minute to preview. Before I realized how much extra time event sheets can add to compile time, it was taking almost two. That was after the graphics had already been cashed. After deleting all of the code from my game and previewing again, the progress bar appeared and disappeared in less than a second. Events, when there are enough of them, take a long time to compile.
I wonder if there is some way to speed up this process, such as cashing event sheets similarly to the way graphics get cashed, except individually, as most of the time that I preview I've only edited one event sheet. I'm not sure how much that would help on large event sheets since AFAIK the event sheet includes simply results in construct pasting the events from one event sheet to another, though.
Maybe if there was some way to be able to cache event sheets so after being compiled once, they can be pasted as a single chunk rather then pasting each and every event, condition and action? Then larger event sheets could be broken up into multiple smaller event sheets, making the whole process faster, since only one of the included event sheets would need to be recompiled. I don't know if there's any other way to optimize the process of compiling events to speed it up, but it sure would help!
Initial preview - since AFAIK in construct 2, games are going to be saved in a way that includes multiple files in one archive, would it be possible to include an option to save the cashed event sheets and graphics as well? It would take up more space, but hard drives are getting so huge these days the amount of time saved would be worth it.
Working with large images - whether it's in the picture editor or how long they take to cache for preview, large images slow down construct a lot.
Undoing on large event sheets - I tried pressing undo on that event sheet with 3500 events. 5 minutes later it was still sitting there undoing. Because of this, I don't use undo any more.
Deleting objects - the biggest speed problem facing construct. I'm not kidding when tell you that when I tried selecting some objects then deleting them, my computer sat working on that for almost 1/2 hour. Because of this, I don't delete objects anymore in the IDE.
Edit: forgot to mention one.
Working in the event sheet - when there are lots of events, edits can take about 2-3 seconds for the screen to update itself with the edit. I recall hearing that the event sheet editor was going to be rewritten in C2 to use hardware acceleration, though, so hopefully that will be fixed.
Can these be fixed for construct 2?