I'm really enjoying this thread, so I'll share my thots/experiences. Sorry, it's not about an ST1100, or an old Harley, but included is an ST and a Harley; hope it still counts. For that matter, there is an 1100, just not an ST1100. Sigh, details, on with the story.
In '90 I bought a leftover (can't remember) '88 or '89 Suzuki Katana 1100. It was Suzuki's sport tourer at the time. Factory hard bags, 1150cc, 130hp right out of the crate, chain drive, oil cooled, even had an electric windshield that went up and down, I don't think much more than 3 inches, about the size of a sheet of letter paper. But man did that thing go - and handle - it was like a sled on rails. Main problem with that bike (more truthfully the problem with me) was that I could not control myself from riding that thing in a very unsafe and illegal manner. It was that powerful, and that smooth. It would have killed me, without a doubt.
So I sold it; only put about 1800 km on it, got what I paid for it, and considered myself fortunate to come away from that experience with only good memories; all of them including big grins. And, ironically, the guy that bought it from me killed himself on it - he was on the wrong side of the road on an uphill curve, had a head-on with a 1 ton cube van. That REALLY shook me up.
Which put me firmly in the field of the motto at the time: SPEED KILLS - PLAY IT SAFE, BUY A HARLEY.
So that's what I did - I bought a Harley. '91 Softail Custom, FXSTC, 1340cc, bought it slightly used, not more than 1500 km on it. Man was that thing beautiful. And it got me to ride in the way a guy should be riding if he wants to survive.
Rode the Harley for 2 years, put somewhere around 50,000 km on it. I was proud as can be of that bike. Never once let me down, took me all kinds of places including Sturgis, tons of smiles and grins. And never once got me a speeding ticket. Because what it did the very best, was all within legal limits.
Sold the Harley, got what I paid for it (that happened a lot back then with Harleys), and didn't do a lot of riding for several years.
I honestly cannot say one of those bikes was more fun than the other. But they were definitely totally different bikes, the fun that they made, the way they made me grin, was for totally different reasons. I do not regret owning either one of them. In fact, while I'm remembering this, I wish I still had both of them now. But I don't.
Fast forward to today; I'm a little more grown up now, and a lot older, and I ride an ST1300. In my opinion, the best of both (of the bikes mentioned above) worlds, at least as close as possible. And it gives me grins every time I ride it.
And that right there is the reason we ride, for the grins we get.