Quick off the mark up to about 30MPH.
Excellent fuel economy.
Handling is scary on open / windy roads. particularly motorways.
Solid mechanicals that can take a reasonable amount of abuse.
Difficult to work on engine (worse on early models)
Variable build quality - no two examples will be the same.
Paint fades / cracks easily.
Highish purchase / resale value = low depreciation if looked after.
Later models have some creature comforts, but still primitive compared to regular cars.
On/Off clutch needs getting used to if new to this type of vehicle.
Variable insurance costs - can be expensive if you do not shop around.
Motorcycle rate road tax = low ownership costs.
Probably not good to be in if a side-on collision occurs.
Harsh rear suspension / trips and falls with ease.
Contrary to appearances, not that easy to tip over in use.
Requires looking after, despite simple mechanicals.
Should last ages if looked after although paint may fade, head gasket can blow if thrashed, gearbox can fail if used unsympathetically, clutch can wear fast unless you keep your foot well away when driving, lights / indicators can develop faults caused by poor earthing if neglected and charging system is normally under pressure especially during winter use.
You need to have a 'thick skin' to drive one of these in order to survive the cruel comments that come from the uninitiated.
Will make you smile when you drive one.
Most of these vehicles are quite noisy when driven (engine / suspension noise). This is exacerbated by driving at higher speed or on badly surfaced roads.
Rubbish to drive in the snow due to the centrally placed front wheel. Equally fun to drive on Cross-Ply tyres if you like skidding on dry roads...
Surprisingly roomy inside if a little narrow - good load carrier though!
Good and bad are equal with these vehicles - just do not compare one with a regular car which it is not - comfort is marginally better than a luxury touring motorcycle (the correct type of vehicle to compare with a 3-wheeled Reliant).
The electrics / cooling system / road noise / high speed cornering stability / durability of SOME of the interior parts / Head Gaskets ARE weak areas (not all vehicles suffer the same issues)
Driving one of these WILL make you a better driver!!!