So far these are the issues/limitations I've come across:
1) Merging cells with formulas causes them to disappear (Big Bug)
2) Named Cells (Aliases) don't exist like in Excel (Limitation)
3) Changing row height causes bizarre effect where active row no longer lines up with row number (Bug)
4) Can not hide worksheet or create readonly cells (Limitation)
5) Scrolling causes borders to disappear (Bug)