I have the QA55E and am generally happy with it. I chose it over the others for the HEPA filter option which I have now fitted*
I don't have the gear to measure the noise level, although I have noticed that the loudness varies quite a bit with position around the machine and height relative to the motor. It's never been so loud that I have to wear ear defenders to do the vacuuming, usually it's the power tool on the end of it that makes me put them on. It also generates its own noise at the end of the hose, just by the motion of the air.
I've had mine a bit under a year now. I have not had any trouble with seals - I seem to recall when reading reviews to buy mine there was a previous Fein machine that was a rebadged Wap, and I think some of those comments apply to that machine rather than the current versions which are from the same Italian company as the Trend T30.
Replacing bags is straightforward, some dust usually gets into the tub but not enough to worry about. I've been told that Fein bags, while more costly, are far better than Trend ones, haven't looked at the Trend ones yet.
If I could change two things about it, they'd be:
1. Make it have anti-static body and hoses - sometimes I get little shocks off it, especially the metal clips holding the motor to the body.
2. Make the auto-switch need more current to run - if I plug in my 110V transformer, it draws enough current when "idle" that the vac runs continuously, even with no tool running on the transformer output. Indeed an 11W low energy lamp was enough to trigger the auto switch on!
If they sorted those two niggles I would recommend it without reservation.
Hope that is of use, any questions let me know,
TigerTurnings.
* Slight palaver involved: I got conflicting information from Fein UK, Axminster catalogue, and a local Fein dealer - the dealer told me that the standard filtration was "just normal" (correct), Fein said that all machines ship with HEPA filters as standard now (don't think mine did) and Axminster says the filtration is "down to 1/2 micron" (don't think that's true of the basic model - though mine was by a local dealer so maybe they're upgrading theirs). Eventually I got a HEPA filter ordered via a local dealer and fitted it with no problems. It was however twice the price of the Trend HEPA filter which appears to be identical (I saw it at a show recently but haven't had them side by side).