I bought a I3 from Costco a few years back. We have 2 dogs and one sheds a lot of very fine white hair. Its everywhere on the floors. The i3 does a amazing job on both carpet and my hardwood floors. I find that the suction is really good and the dirt bin is completely full by the end of the cycle. It will recharge itself when it gets low in the middle of a run and then finish the job when it is recharged. My honest assessment is that this little thing is pretty damn amazing at vacuuming and I honestly couldn't do without it now.
That said it does come with some issues. The first and really only issue is that it does need maintenance every so often., I find that after a few runs it needs a good cleaning. I have to take the rollers out and remove all the hair ( mostly my wifes) from the inside of them as they are long and will wrap themselves around the rollers., also you need to clean the filter every now and then or the suction will not be so good. Also, after each run I need to empty the bin as it is completely full. ( however this last one will vary depending on the level of hair or debris on your floors.. I have a friend who has the one that empties itself and he even mentioned that you still need to empty the main bag and perform cleaning maintenance on it every now and then.
But with all that , I really am amazed at this little thing and its nice to just set it and go and it will do its job. Even high pile carpet gets cleaned pretty good. Every time I empty the bin I'm continually amazed at how much stuff it picks up.