I find the keyboard extends the use of my iPad to replace 80% of tasks I would normally complete on my MBP. The only real obstacle to using an iPad is the file system. If you need to connect to a SMB network share or consume/edit/share MS Office files, it is possible but TEDIOUS. Usually resort to connecting multiple cloud services. iWork is somewhat easier, as the files are stored in your iCloud folder. If I'm just responding to emails, connecting to remote desktops, or managing web apps the iPad is perfectly capable.
Probably worth noting: Because of the way it folds, if you try using the Apple keyboard on public transport, it will topple over. I much prefer the older Logitech Type+ keyboard to Apple's floppy design.