Guess it depends on operations and locations, but I see the KPA-500 meeting some broad operating needs.
I frequently operate portable, for contests, and enjoy a power boost above exciter level power.
I've looked at the somewhat portable ACOM 1010, but it lacks 6 meter coverage and full break-in.
Tokyo High Power? Similar band coverage and QSK issues; can be a little more portable.
The Ameritron (MFJ) solid state amp? Again 6 meters and QSK are lacking. Also, I've had too many QC issues with that company's products. YMMV.
So, the '500 appears to offer a very compact (K3 size, 22 lb.) package, full 160-6 meter coverage and QSK--all with internal power supply. Sounds like a traveler's delight to me as well as being a medium-power level amp for home use.
What's not to like? I hear wishes for a built-in antenna tuner. For some people that's a need, for others a non-issue. When I use a tuner it's a Johnson matchbox with ladder line into the shack. If I'm using a coax-fed antenna, I will work it, and work it, work it some more till it is resonant and no tuner is necessary. That's me.
Is 500 watts not enough? For the rarest of the rare DX, for top-ten contest results, maybe not. But it is a better-than-5 dB improvement from exciter level. There were recently expressed wishes from some on this reflector for a 150~200 watt PA. Here's an amp that, with reduced drive, gives that sought-after power output level. The 500 watt power level is also compatible with the power limits in many European countries.