I bought mine during Amazon's prime sale (about 1.5 months ago). Pecron had their equivalent sale as well.
I don't have any long term usage comments. For the 80% charging issue, I have read that you may need to drain / use the unit until the battery is empty then charge it up to full. That allows the BMS (battery management system) to re-sync things.
For about 0.45 cents / watt for the battery size, you take and accept all the good and bad.
My biggest gripe is wishing it had wifi so I can remotely check on it and run things. I don't think any or very few companies have a wifi enabled solar generator. I know pecron has their E1500LFP (can't remember actual model) but it has wifi and built AC charger. It ships later in September though.
I don't mind the external charging block since I charge by solar or if I am at home, charging block is fine. Efficiency appears good at high 80s / low 90s. It heavy but what 2kwh unit is not heavy. The dual 600w (1200w total) solar input is very good to have.
I cannot build a similar unit for the same price. Only when you go large, much larger like 10kwh or 30kwh does it make more sense to build or buy a kit to assemble.
To recap, I like it and will keep it. For camping, the boss (wife) has a lack of appreciation for power hungry devices and having something that can run a grill, coffee maker, hot water kettle, etc is great to have. Obviously not at the same time.