So what about those caveats? The most pertinent is that while the 780 will take the chore out of vacuuming it does require some 'Roomba proofing'. For example, while the 780 won't damage cables if left around it will still drag them about and should you have particularly light doors it can bump into them after tracing along walls accidentally closing them and locking itself in a room. This is quite comical at first, but unless you want one spotless room every time you come home we would suggest investing in some door stops. Of course there is some maintenance too, but aside from emptying the bin or using the supplied tool to clean the brushes every so often it is largely hassle free.
All of which leads up to cost. This is always the biggest caveats with any robotic vacuum and given the 780 is iRobot's flagship model it is doubly so here. Should you pay it? It depends entirely on circumstance. In a multi-floored house the Roomba's efficiency is greatly reduced (unless you are going to constantly move it or buy more than one), but for those with the means and a home or office largely on one level then yes. £450 is a large investment (£50 off its initial £500 RRP at some retailers), but it actually works and using daily cycles means your property stays far cleaner than it would using your conventional vacuum just once a week.
For the first time we feel able to say a robot vacuum truly lives up to its title. This comes through the Roomba 780's combination of improved navigation, increased suction and vastly better battery life. Yes some effort to required not to leave items needlessly lying about, yet at worst they will be spread around not damaged and remember to chock light doors. Don't tell your friends how much you paid, because the 780 will become your most guilty pleasure.