It's as effective in cleaning my hardwood floor as my Roomba. For testing, I sprinkled the debris I got from my roomba's reservoir and the Eureka was able to get all of them with no issues. It has several modes of cleaning. I've mostly used Mode 1, which will direct the vacuum to clean the edges only and Mode 4 which will direct it to clean in zigzag mode.
On carpets, it's not as effective as my roomba. Some debris was left after the Eureka passed through the area. I'm suspecting it's the motor power or maybe the brush, I'm not sure but it's not as effective in carpets than my roomba. I can see it bouncing a bit in the carpet which might affect the cleaning or sucking of debris by the roller brushes.
One of the things I liked as well is how the dust bin was designed on the Eureka. Unlike the roomba which has the dust bin on the back edge and slots from the side, in the Eureka, you need to open the top lid by pressing it. The dust bin is inside and there's a handle you can use to pull it out. Again, better designed than the roomba. The dust bin is also a bit bigger compared to the roomba which means it can vacuum longer before you need to empty the bin.
Overall this is really a good buy. Comparing the price which is $1000 cheaper than the roomba, if you have mostly hard floors (hardwood, tiles, etc) this will clean it with no problems at all. The $239 price is low enough for anyone to just buy and try it out. I was pleasantly surprised on how good it was. Very happy with it.