Got my hands on one of these today and I'll have to agree to some extent, although my experience was a bit nicer. - especially on the airband as compared to the small G6.
For me, sync is a toy that I ignore. I haven't come across a budget receiver that does it right anyway. Even the sync in the canonical Icom R75 is being dropped.
I didn't run into the overload conditions that you experienced, and find SSB/AM generally nice to use. Audio filter for narrow is ok, but still a bit too bassy. Any receiver that has AM / FM broadcast capabilities always seems to try and make HF "high fidelity" and misses the boat.
Airband ops: ok, this isn't a scanner.
Noticed that for airband there seems to be a fixed level of sensitivity / attenuation as the dx/local switch has no effect. The external antenna jack doesn't seem to be working on airband either. So we're stuck with the whip.
The manual mentions using the whip fully extended for airband, although I usually like to push the elements down to about 23 inches or so. In this case, I found the best sensitivity for airband was with TWO of the upper elements pushed back in. Not a bad idea since the whip is extremely fragile.
The lack of a squelch is mitigated somewhat by the fact that the receiver is MUCH quieter than the little G6, and in fact is now actually usable when sitting on a freq. There is a little bit of background noise, but there is enough audio power to let the radio sit across a desk / room and hear the aircraft comms without going nuts listening to a lot of noise in between transmissions. Not a squelch for sure, but I can actually use this thing now.
The lack of scanning capability is not a big deal, since if I want to scan I'll grab a scanner.
In addition, the up/down arrows use a frequency spacing of 10khz from the AM broadcast band, instead of the standard 25 khz for general aviation! You can get around this by just knowing the exact freqs ahead of time, or using the VFO - which is cool for those with 8.33 khz spacing. However, for those who don't know the aircraft band, they are going to miss a LOT of the action if they rely on the radio to step through the freqs with the arrow keys.
Grundig: if you are going to promote airband capability, provide a squelch and at least use the right frequency steps.
Maybe in a future upgrade? Scanning a page of aircraft freqs might be nice, but don't know if we'll ever see that in a typical HF portable.
Also noticed the weird signal sound when using the supplied charger. Substituted a higher-quality charger and the same bizarre sound is heard. So, for now, I'm only running off batteries and using the adapter solely to charge the batts if I have to. I don't know what's up with that.
I've also tried using just collapsing the whip a little bit instead of using the dx/local switch as an attenuator alternative and that works well sometimes too.
Overall, for $150 not bad - but I would have rather had them put the money and r/d into making a better sounding *communications* radio with tighter specs rather than promoting RDS and Sync.
At least the airband is tolerable, unlike the G6 "aviator".