I have a mare by Art Deco who is very similar to the horses described by the earlier posters (beautiful, athletic, sweet and loving–on the ground–a talented, powerful jumper, brave, sensible in stressful conditions, and an awesome competitor…HOWEVER, she is spooky, hyper-vigilant and hyper-reactive, and has to make almost every ride a challenge (at HOME! only, where she is “Supreme Alpha” over all the other horses–not at competitions, where she defers to me, and is at worst, fussy and distractible–but performs well consistently…though I have to carefully manage her warmups, since she freaks out when other horses get too close to Her Majesty :rolleyes:)
She will be absolutely lovely on the ground: relaxed, calm, submissive, sensitive (in a good way), sweet, and eager to please. Her ground work (which I’ve done a lot of) is wonderful; a dream! However, the instant I throw a leg over, she’s all of a sudden in “WHAT THE HELL IS THAT???” mode, spooking at the mounting block, jump standard, barrel, human, car, leaf, cat, other horse, etc., etc., that not only has she seen 100+ times, but that she had ignored completely not 10 seconds previously. :sigh: Spooking in a very melodramatic fashion, mini-bolting, pop rearing when corrected, etc…Luckily I have quick reflexes, and am able to correct her, stop her, bend her, displace her hindquarters, and put her in a “head down time out”, which I have developed as a response to her constant testing and “faux spooking” behavior…(It seems to calm her down and re-focus her, as well as serving as a correction; as another poster mentioned, I am constantly working on getting her to “tap into her thinking brain”, and override her reactive brain. Over the years, she has progressed slowly in terms of “seeming to get the picture”, and now knows to shape up when I verbally correct her, though I continually have to “remind” her that she’s not in charge…it’s quite emotionally exhausting, at times!)
In competitions, though she can be a bit of a trial in dressage (tense, holds her back, want to look around), she is a dream to jump (and I have taken a LOT of time; she’s ready to go Prelim in eventing in a couple months, with LOTS of preparation–and has talent out the wazoo), and I never doubt her; she’s a fantastic partner…
And she’s my heart…:sigh: A total love, licks you like a dog, is SO expressive…
Plus, she has fantastic feet, and has NEVER been shod! She’s 10, and if I can run her Prelim without shoes (being careful with the venues, and scratching if it’s too slick), I don’t see a reason to shoe her, since she has excellent (4WD-worthy) traction–in all conditions. 
Needless to say, I have mixed feelings, but relate to most or all the previous posts; this mare has a home for life with me (I am a lower-level pro, and readily admit that she is SO not an ammy ride! :eek: She’s lucky I have her, because otherwise she would have scared someone–badly–and would be in a broodmare band, instead of fulfilling her potential ;))
ETA: she has a very strong will, but luckily, so do I…:winkgrin:
(And I don’t know about the dam, who was a TB…but in terms of the influence of early training, when I got the mare at 5, she had just had a couple of months of real training U/S (and hadn’t been shown or jumped or exposed to new stimuli), so I did the vast majority of training and exposure, introduced her to ground exercises and TTEAM stuff, walked her over terrain in hand, started her over fences, and REALLY took my time…which I believe in doing in any case, regardless of the horse! :yes:)