The FRG-7700 is not a bad radio. It is not particularly good (when compared to really good radios, like the NRD 525, Drake R8, or something), but not bad. It competes well with other receivers in the same price class and age, it was a mid cost entry / mid level desktop in the day. I have owned several over the years, and still own the original one I bought new in 1980.
The review on eham that states low sensitivity, wide filters, and overloading is valid, but the question becomes, what was he used to? I find it hard to believe the two he lists, the FRG-7 and the R-1000, were any better.
The FRG-7700 sensitivity, by spec, is about 0.5 uV in SSB mode in the HF range. The Sherwood Engineering tests showed their example at about 0.2 uV, my current copy runs about 0.24 uV for 10 dB S/N in 2.7 kHz. This is not bad, but certainly not top shelf. Fortunately raw sensitivity is not often an issue on HF, where you tend to be noise limited, not sensitivity limited.
The FRG-7700 does have limited filters, 3 filter widths in AM (12 kHz, 6 kHz, and 2.7 kHz), one width in SSB and CW (2.7 kHz) and one width in FM (15 kHz). This amounts to a fair selection of usable bandwidths in AM, an adequate "normal" filter in SSB, and a far too wide filter in CW. And while you can always change the filters out for different ones, there are not multiple selections for each mode, so you still only end up with 3 in AM, one in FM, and one for both SSB and CW. And if you put in a nice tight CW filter then it makes SSB almost unusable. From the filter aspect the radio was pretty obviously aimed at the SWL primarily listening in AM, that wanted SSB, CW, and FM capabilities also.
As for overloading, yes, I have seen FRG-7700s do that, but typically in pretty extreme situations. While they can overload I have not seen it as a big problem with them. And if / when it does overload you can crank down the gain. There is a front panel variable attenuator, and there is also a back panel local/DX switch.
The FRG-7700 is an in between tech radio, a world that really only existed for a few years. It is an all solid state radio with a digital display, but it is not a digital radio. Yes, it has a digital display, but the radio itself and all the frequency sources inside it are analog (unless you have the add on external memory module), using crystals, PLLs, and similar sources. The digital display is a digital frequency counter that is used to measure and display the analog VFO frequency.
The FRG-7700 is a decent desktop that works well, if not a stellar performer. If you compare it to top end radios it will come up short, but if you compare it to lower end desktops, like the Radio Shack DX-302, it is quite good.
T!