Wheeled Travel Packs have a very rigid back as the handles go the length of the backpack when pushed in, which enables the whole front of the backpack to be hinged on clips as with the Sky Master Series and Fast Track Series. The zips open all the way round like a suitcase. Those who have travelled with a top load only backpack will realise just how useful this feature is. There's nothing worse than having to empty the entire contents of your pack to get at a piece of equipment you packed at the bottom of your toploader rucksack. The wheels also mean that transporting the backpack is a great deal easier than normal. It considerably reduces the strain on your upper body when you can simply wheel it around town! For those backpackers that like to go off the beaten track then the harness system is well padded and comfortable and gives good support.
However, if you plan to do a lot of trekking where you will be carrying the pack most of the time then forget the wheeled backpacks and choose a good quality travel pack / rucksack instead. Have a look at the Caribee Mallorca or Jet Pack available here on Amazon at the Adventure Avenue store.