Yes I have all three, iPhone 3GS, MacBook 13" aluminium and an iPad.
Do I really need all three, probably not. The iPad was a must buy gadget, but it has become my primary bit of kit. The iPhone has pretty much been reduced to just being a phone, once I played Angry Birds on the iPad I couldn't go back to the iPhone. Same for FB,twitter and email.
Feel sorry for my MacBook it's been neglected and we were so close, but times change😉 the MacBook is my store for music, photos. I use it to rip and burn. And it holds my material for work. I teach at home so the MacBook has the audio tracks and print outs etc.
It's the battery on the iPad that is so amazing, I can surf for ages sitting on the bed or sofa. Do still take the MacBook to bed to watch BBC iplayer, I have to use a VPN and openvpn isn't available for the iPad. (pptp VPN on the iPad can't hack the distance to the UK). So in this respect I feel like the head and shoulders ad, " still taking a shampoo and conditioner in to the shower"
If I had the cash, I think I would readjust my line up, losing the MacBook adding an iMac, I could watch iplayer on a bigger screen. As for the iPhone well I won't be upgrading to iPhone 4, can't justify it. Might go to iPhone 5 but not in a hurry.
As I said in a previous post I hope in future to see an iPad-pro that merges more of the MacBook Air into the iPad. Hook up a big screen, keyboard and mouse when needed, unhook to lounge around the house or the coffee shop😉
There is a lot of overlap in the products, but something for everyone.
Different strokes for different folks.