I've had my off-track Thoroughbred for three years and adore him

I'm a complete TB convert since I bought him.
As has been said, it completely depends on the horse. Mine lives out quite happily, is barefoot and stays out in all weather. Some just wouldn't tolerate it. Mine has been a complete swine to fit a saddle to - others are not a bother. I had a horrible time getting his shoes to stay on, which was my basis for going barefoot, but he did require several months off work to condition his feet, and it's taken a year for him to have good, healthy feet.
Thoroughbreds, as a breed, seem to have a tendancy to be a little highly strung, a pre-disposition for stable vices, and can be complete loons. They can also be notorious for trying to keep weight on them and typically have quite a fine coat and thin skin which can lead to ticklishness. There's always exceptions to the rule

so each one needs assessing as an individual, but it's worth bearing in mind.
The other big "thing" with TBs is whether they have raced. Re-training an ex-racer is a big job and not to be taken lightly, whereas a TB who has never raced or who has already been retrained is another kettle of fish altogether. A good Thoroughbred is usually very responsive, intelligent animal and I have to say I get so much pleasure from the relationship I have with mine.