Check out the full review on the eHam site.  This is an exerpt from it: 
The noise-floor of these sets are not comparable to a DE-1103 which pretty much hammers down the noise. So one is left pulling stations out of the weeds. And the PL-310 does rather well at it on AM-BCB. And that noise floor due to propagation and local influences like Sub-Audio-Heterodynes (aka flutter) can raise havoc. There is a function of the AGC circuit called Soft-Mute, and will engage/disengage on weak reception. Coupled with "flutter" this makes listening unplesant with a noted "pumping" sound. Fortuneately, the design-engineers allow that offsetting the tuning by 1 kHz will shut-off the Soft-Mute. One has to raise the volume a level or two. In the 3 1/2 years of building, Tecsun has not put in a hard-wired On/Off for this function. Outside of the AM-BCB its rarely needed, and that is probably the answer.

As other reviewers have pointed out the audio-bandwith selection and filtering is superior at this price-level. The Low IF of about 45kHz keeps SW and AM-BCB imaging to a minimum. Kudos to SiliconLabs for designing this after the Sony analog version. Low-IF is the way to go.

Where the PL-310 really shines as does its siblings the PL-380/606 is on FM. Very hard to beat in general, and seems to be limited to sibling rivalry at this price level.

SW holds it's own against others under $100, what the antenna lacks the BW selection helps. What these DSP sets don't have is SSB. And thats a turn-off for most Amateur Radio Enthusiasts. And is very much the reason for a 4/5 rating. The PL-310 is just not quite everything, but what it does, is well done.