Im sure many will have opinions but...
Have you read Chris' previous post?
http://www.vacuumland.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?23791
Pros:
Good suction
Easy to push
Long cord
Relatively low noise
Low running costs
Flat to the floor cleaning
Easy to fix
Turbo brush can be used on the X1.1, X4 and X5 models.
Lengthy guarantee
Cons:
No brush roll on/off function
Can fall over when instructions haven't been read properly.
Sensor won't adjust properly on thick pile carpeting.
Short hose on board - extension hose could be bought if doing stairs.
No dusting brush on the X1.1 as standard.
The dust bags are the lowest priced in terms of capacity and amount - you get almost double for the same price as Miele's 4.
The filter roll can last up to 32 dust bags and 16 to 20 bags if buying the charcoal filter for pets. An additional filter goes on top of the motor,
None of the SEBO X series deep cleans deep into the pile - which I'm quite happy about - and SEBO do advertise that the X series "gently cleans" for good reason (which many seem to forget and then moan that it never goes deep enough), but the design is as such the brush roll design reduces brush wear and carpet wear.
Unlike other brands you can choose the standard roller brush or a soft roller brush, and this also applies to the Felix.
As I have wool short loop I have to be very careful with my uprights as wool short loop is very easy to damage if it is allowed to be cleaned with deep "dirty fan" style brush rolls - one reason to why I may well adore my Vax VCU02 but have to be careful with its use.
An X series though is good as an alternative to what you have in your collection, Jord. Most owners get annoyed with the short hose on board and its location at the top means it will fall over when used - unless you go by the INSTRUCTIONS and hold the hose with one hand whilst using the end hose with the other hand.
So many moan about the X series because they don't read the instructions or the info online about them - but I can tell you - they surprised me when I was a Hoover collector - the X models go on forever - and in this day and age in the UK, that's a hard aspect to find, these days.