Only left me stranded once since 1994, and that was only a blown lower radiator hose.
This is not a pampered garage queen, I drive it like it's Japanese.
I rebuilt the engine at about 80k, rebuilt the trans at 50k (needs it again, weak synchros), put a water pump on it a few years back, and went through a rash of generators early on, but the last one has gone tens of thousands of miles without incident.
Next on the list is the front shocks, as the car has started to oscillate the wheel after hitting hard bumps.
There was no category for "cute" on the list, so I'll provide one here, 10/10.
Everyone loves this old car. Little kids go nuts for it, chicks dig it, and old men recall their British sportscar loves lost.
It has proven to be incredibly forgiving of my limited mechanical abilities at first, patiently teaching me how to own a British car without harshly rebuking my missteps with breakdowns or wallet cleaning.
If it's speed you're after, then dig 25 grand deeper into your bank account and get a Tiger; this ain't your car. Rather, it changes your outlook on driving after a period of time, making you ask "why's everyone in such a rush".
Reliability is near bulletproof for a car this vintage, and it's reasonably easy to wrench on, if a little compact under the bonnet (certainly no worse than a TR or MG).
Spares are no problem for normal wear items, but trim parts are getting dicey; I'm in the market for a hubcap for a Series I, still.
As I said in the repairs list above, I drive it like it's Japanese, everyday in the summer, and usually only do routine maintenance, and something more major every five years or so.
The comfort level in the Sunbeam isn't great for long trips, as the seat is a bit near the floor, so your legs will feel awkward with no comfy place to rest.
The rear axle whines loudly in mine, as it has for 60000 miles and 16 years. This isn't a big deal with the top down, but when the hardtop is on, you can barely hear yourself think.
The soft top is a real PITA to unfurl or stow; it's usually easier to get wet than deal with it.
The heater is better than you'd expect in a Brit this age, and it even has a defroster.
All in all, this is a car I'd highly recommend for someone wanting a British car to use and not spend a fortune on. It's better built than a Triumph, cuter than most MG's, and nobody will mistake it for a kit.