Well there are plenty of other uprights on the market with so-called auto adjustment that are hard to push on carpets. My Hoover Slalom is a good example. Only time it is light to push is if the silly suction air outlet valve on the underside is opened and then pick up is impossible the first time around.
If we're going to go down the "main selling point" of many a vacuum cleaner, especially an upright, then there are a few inaccuracies when it comes to cleaning hard floors, alone. Beater bars for example are a general no-no because they can mark hard floors.
Furthermore, if you use the "hard setting" on a Hoover Purepower upright, the setting lifts the floor head completely off the hard floor and dirt gets little chance of being actually sucked up with the beater bar constantly spinning. The Purepower isn't alone here - plenty of manual height adjustment vacs do this, which isn't exactly helpful to the owner.
Frankly I'm shocked to hear about the SEBO's inability to clean deep down. I've never found the SEBO not to deep clean AND not protect the carpets I use my vacuum on. The main selling point of the X is that is it lightweight to push DUE to the sensor adjustment and it is for carpets - hence why the Felix was introduced with a manual height adjustment and brush roll on/off function.
Infact, when it comes to performance, very little is said of protecting carpets - not many brands will go to the bother of designing a brush roll that protects a carpet as opposed to ripping tufts out of the pile - cue our old Dyson for doing that.
I find the suction strength to be pretty good on the SEBO uprights - particularly when the bag is near the end and there's still enough suction - this is more apparent with the synthetic dust bags of late rather than the paper ones.