Re: U.S. has used Harriers...
"And if you;re using the Harrier in a non S/VTOL manner, why put up with the other compromises like the brick-like aerodynamics, the heavy airframe, and the severely anhedral plan that contributes to hugely unstable handing?"
The Harrier was designed for Close Air Support (CAS) & Fighter Reconnaissance (FR) from front-line operating bases and this dictated most of its design features. CAS requires low altitude performance and FR requires manoeuvrability.
As far as I'm aware, the Harrier is always operated in STOL mode (rolling short take off and short landing) from land bases because there's little to be gained from conventional long roll take offs and landings. S/VTOL (rolling short take off and short/vertical landing) is used from ships for obvious reasons.
The Harrier has exceeded the speed of sound in a dive (the supersonic P.1154 was cancelled) and everything I've heard about them indicates that their manoeuvrability is generally very good and their acceleration, perhaps unsurprisingly, is exceedingly good. It is, apparently, an easy aircraft to fly but vertical landings, whilst not difficult, do need regular practice - same as most other aircraft really. Because it's designed to operate primarily at low altitude, thanks to the CAS requirement, it will usually be on a par with most other aircraft it's likely to encounter, which are designed to operate at high altitudes, and their engines are just as thirsty at low altitude as the Harrier's Pegasus.
As for weight, the GR3 came in at 13,535 lb empty/25,200 lb MTOW rolling Short Take Off (STO), the AV-8B comes in at 13,968 lb/31,000 lb MTOW (STO). The (not really comparable) F-16 weighs in at around 18,900 lb empty/42,300 lb MTOW, the F/A-18 23,000 lb empty/51,900 lb MTOW and the (cough) F-35B 32,300 lb empty/60,000 lb MTOW. I've included the F-16 because it's a roughly comparable weight, but note that it lacks the much heavier landing gear that carrier borne aircraft need - in the light of those numbers I find it difficult to regard the Harrier as overweight - it's just a smaller aircraft and carries a proportionally smaller weapon load.
The Harrier's Pegasus engine dictated a high mounted wing; without anhedral it would have been too stable for its intended CAS/FR role.