I have used about 15 different Oreck upright units of various models: Commercial XL, 2 XL-21 series, pivoting head model, Dual Stack Commercial, several XL Ultras. Every single one that I have used has given me an allergic spasm within just a few minutes of use!!! Many of the units had just returned home from their included service annual checkups from Oreck or were refurbished by collectors or new!!
Additionally, these units weigh 8-9 pounds, I think the Dual Stack Commercial unit may have weighed around 15 pounds. All of them feel like pushing bricks across the carpet. The brush roll does nothing to propel them at all on any of the models that I've tried.
I have found cleaning mediocre. The XL-21 does a better job but still not great. Noise is loud on most of the models I have found.
The filtration issue I think comes from poor sealing around the bag and not being powerful I think the brush roll kicks a lot of dirt up into the air and the airflow isn't powerful enough to catch it all. In comparison I have Hoover Celebrity canisters, Eureka B bag canisters, Hoover A bag convertible with vinyl bag, and have used TONS of vacuums over the years none of those Hoovers or Eurekas would be rated very well for filtration but I have never experienced any sort of allergic attack to them during use!! The Oreck and also the Garry Vac give me the same allergic reaction!!!
I have tried the Riccar SupraLite and although a little loud, it glided itself across the floor with ease, the floor looked very clean, construction seemed significantly better than Oreck and I had no issues whatsoever with filtration and being able to actually use the vacuum!!!
Oreck had a power nozzle canister years ago known as the DutchTech series. There was a green unit and a white TOL unit. The second generation of these canisters came equipped with a Wessel Werk EBK 340 power head. Very nice, powerful cleaning canister vacuum cleaners!! If you ever see one of these, I highly recommend it. They are very powerful and quiet with great filtration. But their uprights I can not recommend at all!!!