Let’s discuss “What is your biggest spreadsheet pet peeve — and have you found a fix for it?”
My biggest peeve is with google sheets - the cell protection is absolutely awful. I wish it could be exactly like Excel cell protection. No fix for this unless I switch to excel!
Oh this 100%! I’ve started things in sheets, but switched to excel, because of the cell protections among other things. There are definitely quirks on both sides where the other program is better. With tiller though, I don’t seem to have any issues for my needs.
I know this is a Google Sheets issue, not sure about Excel, but inserting a row above row 2 anywhere will adjust the range for a data validation rule on another sheet that’s referencing the sheet where the row was added. This messes up the list of categories available in the Category column in the Transactions sheet for customers all the time. Their newly added category in row 2 won’t show in the dropdown list! 
Unfortunately, it’s a Google issue, not a Tiller issue.
The workaround is just not inserting rows above row 2!
Oh I never thought of that being the reason I was having issues when I was doing some copy pasting. Fortunately I now have a plaid connection for the bank I was having to manually add - it was much faster to copy/past the recurring transactions as I had about 30. 
Oh Hotkeys and short cuts from excel that are much more unwieldy in sheets ie the ctrl + and ctrl - for adding and deleting rows. and the precursor the shift + space and Ctrl + space to select rows and column you have to hit twice to get everything.
but fixes depends on the browser and other extension you might have added. Basically the easiest fix is to just get used what ever google has integrated 'cause installing other extensions or switching to excel 365 will create different issues.
oh and since i use lots of formulas but don’t really understand gemenai tends to insert comments to explain that it does, but sheets will bug out with those so need to delete.
The main benefits of sheets is that it’s free and already cloud synced. otherwise i’m sure the vast majority would’ve switched to excel.