I have several OTTTB's plus have looked after OTTSB's.
Lovely horses all of them.
Pros: Have seen most everything and are used to crowds, noises and pressure situations.
They are very athletic and can turn their hoof to anything and generally be very good at it.
Cons: They come with baggage. Some no more that any other pre-loved horse but others with quite a lot.
They CAN be difficult to keep weight on but by no means all of them are (I have 2 which when younger were real fatties and I had to watch what they ate!).
Generally have crappy feet, but they do improve with time. When mine are just running around the paddock they are barefoot.
It takes them a while to become 'normal' horses. Some of mine have been 6 months, while one took 18 months to 'turn the corner.'
We have had some magic moments with our crew and they have given my kids (when they were home and competing) a fantastic and successful time (everything from dressage, jumping, trails, sporting and campdrafting to whatever the kids imagination demanded). They have mellowed into old age beautifully and I love them to bits.