I have a 5-year old 24" iMac and also an iPad Air. But the iPad has been my most vital device for the last 3 years. Used to own the first iPad and followed by the iPad 2 as well.
The reason why I still do not own a MacBook Pro or MacBook Air is because I have made the iPad into my 'laptop'. Well, almost.
The iPad is not just a consuming device, I do my work with it on a daily basis. I have a Synology NAS drive that I can remotely access all my documents on both the iPad and iPhone, depending on what is most conveniently within reach at that point of time.
With so many apps in the market, it has made my iPad the centre of my workstation and also my main entertainment device.
These are some of the apps that I have been using for the last couple of years:
1) LogMeIn - remote access my iMac from my iPad when I am away from home.
2) Air Video - streaming movies from my iMac to my iPad and AirPlay to the AppleTV.
3) Evernote - syncs my notes across all my Mac devices (iMac, iPad and iPhone).
4) GPlayer and VLC Player - I am using these 2 apps together with the Synology NAS drive's apps, mainly DS File or DS Video. Movies are streamed and opened using either of the apps and AirPlay out to the Apple TV.
5) DS File - this is a Synology app that lets me access all my folders and documents when I am away from home. No problem even watching a movie from here.
6) DS Video - the name says it all; all my movies and series are easily accessed through here. It opens in any file format, as long as you have apps such as GPlayer or VLC Player.
7) DS Download - I can download torrent files right off Pirate Bay and it starts downloading right away. Once it is done, it stores directly into whichever folder I assigned it to. And this means it goes directly into my NAS drive, without the need to switch on my iMac.
8) DS Audio - my entire music collection is all in here. Whenever I add a new album, it indexes and goes right into DS Audio automatically. There is no need for re-arranging them. Plays albums streamed to my iPad or I can even download the album into my iPad and listen to it offline. I usually will play albums and send it out to my Airport Express that is hooked up to my speakers.
9) FTP Sprite+ - I am able to upload movies, series or music albums from this app directly into my FTP server.
10) Smart Office 2 - I can draft out contracts or do write-ups from this app, saves it and then transfers the saved document via Open In DS File. Recently, I have been using Pages more often though.
11) iZip - unzip folders and extracts it from this app. Once I am done, I can transfer the contents directly into the DS File app.
12) Viber - my alternative to Whatsapp when I am on the iPad. Works very well and I can even make a phonecall or two, provided I am on a very stable connection and the other party that I am calling needs to have a strong signal as well.
It really depends on how deeply-integrated you want the iPad to be. But with the help of devices such as the NAS drive and also with third-party apps, it is narrowing down the perception of the iPad being simply just a consuming device.