I purchased this set for my small rental business. "Shure" brand has its authority and there are probably no problems with clients when choosing wireless microphones for their events.
Of course, as a sound engineer I do feel difference between BLX and ULX, SLX series, but the price also matters!
In future I'm planning to purchase Sennheiser systems because they have microphones with metal shells even in beginner series. It looks far more reliable!
To sum up:
Radio interference problems - never experienced when following the manual.
Sound quality - appropriate for BLX series.
Reliabilty - I would never try to drop the mic to the floor! It's just fragile plastic!