It's not bad, but I would pick a Mac over iPad for Numbers any day. It actually has most (if not all) of the functionality, but you have to go through the iOS UI. My biggest complaints are:
- Everything has a slow (relative to Mac) animation, since it is a touch-first UI. For example, I can easily get it to drop key presses when I invoke the Find window by pressing ⌘F and immediately typing, because it doesn't record key presses until the animation finishes.
- The statistics previews when you select cells are unavailable. You have to autofill into a cell to get statistics.
- Autocomplete has a tiny window, the same size as on iPhone, so most of the suggestions are cut off. Even when your iPad is in landscape or using an external display. It's ridiculous.
- If you use the Stepper cell format, you cannot type into it even with a hardware keyboard. You can only use the up/down arrows to cycle through numbers.
- Not all keyboard shortcuts are implemented. For example, Collapse/Expand Group (⌘8/⌘9) is there, but the related ones like ⇧⌘8, ⌥⌘8, ⇧⌥⌘8, etc for expand are not.
- Selecting cells can be a bit wonky compared to what you might expect from Mac.