I have a canister and an upright, the C3.1 and X5, respectively. These machines are wonderful. They compare well to Miele and Simplicity/Riccar. The fit and finish is excellent and precise. They are very quiet but very powerful. They clean very well. They have excellent filtration and offer a standard S-class filter or an optional HEPA filter. They have both pre-motor and post-motor filters as well as excellent bags. The customer service for Sebo is very conscientious, and the marketing director for Sebo USA used to keep track of comments on the old vacuum forum.
Sebos are expensive, as are the bags. The HEPA box is over $50, but I think it's worth it.
Patrick