Mark, Sorry to hear that the hose is giving you a problem already but, its great that the seller is sending you a new one! I feel like its one of those things that you just shouldnt talk about because you may jinks a good thing that you have going at the moment.
As for the bags, I've owned many Electrolux machines over the years, various uprights and canisters and I have always used Genuine Electrolux/Aerus bags in my machines. The way I see it, for me the price is right for the genuine paper Lux bags, so I wont switch to an after market bag since I have never had a problem with the bags themselves. The only non-Electrolux bags that I do use, not really after market, are the Perfect PowerTeam HEPA C-type bags. Obviously because they offer better filtration and airflow, overall a higher quality bag in my opinion.
As for the power nozzle not having the same amount of power on all three speeds, you may be 100% correct. However I just finished using mine and I was thinking about what you said. I love that I can set the unit on "low" and use it on something like the small bathroom area rugs which are usually a real pain to clean since they have a rubber backing and get sucked up into most power nozzles. Anyway, I used my Renny on a dense wool area rug and played around with the motor speed. I may be wrong but I think that you may notice that the nozzle seems to have "more power" on a lower speed becuase there is less drag on the power nozzle motor. With greater suction the power nozzle seals itself more firmly to the rug (I have several very dense area rugs that are truely a PIA to vacuum, even my Diamond Edition is difficult to use on them with the TechDrive engaged) therefore creating more drag on the motor, hence it seems as though the motor is not moving at the same rate as it does on a lower speed (which it probably isnt, buts the motor isnt at fault). Again, this is just my own theory and I dont mean to discredit what you said in any way, but I never noticed any difference until you pointed it out, and in my own home I can attribute this change in power not to the machine but the rug itself.
I hope your Renny is back up and running in proper order soon!