We have both and

them both! Got them both on woot a year or two apart (roomba $149+5s&h; scooba $99+2.5s&h - split order).
The Roomba works best when you run it frequently. I have it clean our kitchen twice a week and the other rooms once a week each (downstairs only). It is busy 4-5 days a week and our floors always look nice. We have all cork flooring on that level and the edges show the cat fur and dust whenever I slack off on running the Roomba. Some area rugs are okay to leave down and others need to be picked up. The key is if the rugs stays put or rumples. We have both and I only pick up the ones that rumple and the Roomba gets stuck on. As others have said, it does a good job of going around piles/items if they are secure type items. Loose items will either get pushed around or sucked up, depending on what they are. It isn't magic, though, so don't expect it to be.
The Scooba does a light pick up of dry debris right before it sprays down the liquid cleaner (I use plain hot water, but you can use vinegar and water or the Scooba cleaner). Cleaning it out is not gross to me and is super easy. You just rinse out the two rubber-plastic contraptions. Stuff doesn't build up or have any crevices to get nasty in on those two pieces. I also remove the brush piece and rinse that off and leave everything to dry. If you do it every time, it is quick and easy. If you leave it to build up, the section between the two squeegee parts on the brush piece can get a little icky. It runs for 45 minutes on one tank and the battery lasts for two tanks (on my model). I can do my kitchen on one tank (12x14, I think) and the powder room and foyer on another tank (downstairs on one charge). I can also do the upstairs bathrooms on one tank (I mix that in with one charge). I clean after the complete charge cycle is done, not after each tank unless I am only doing one tank that day.
Both items do a good job if you plan to run them frequently. They aren't perfect and shouldn't be compared to hands&knees mopping or a central vac. The way I see it is this: If you are cleaning regularly in depth, then these tools probably aren't going to give you the same level of clean. However, If you are NOT cleaning regularly in depth, then these tools will give you a new level of clean and appreciation for "robots".
