Shared memory? Are you talking about chip RAM? Even with the chip RAM limitation, it did not affect the A1200 abilities as much as that in a 386, due to the Amiga multi-tasking operating system... something that Windows 3.1 and OS/2 could not provide.
OS/2 actually provided the best multitasking capabilities of any computer of the day, including the Amiga. Even by today's standards, it was practically crash-proof. Amiga could still have a bad application bring the system down; but in the world of OS/2, everything was running isolated, and nothing could have direct control of any hardware. Sadly, it, too, had gone the way of the Amiga.
It all boils down to this. Does a person go for the entire package - hardware and o.s. - or does a person go for just the hardware? You went for the hardware. I went for the entire package, i.e., in 1992 no way would I go for hardware, no matter how slightly or majorly superior, if the o.s did not deliver and was not elegant. Windows 3.1 and OS/2 did not meet my standards (ooo, Windows 3.1 was awful). To compensate for the Windows/OS2 liabilities, you had to keep buying newer and newer hardware -- hidden but added costs.
Actually, for many people it boiled down to this: Does a person buy a computer for the sakes of having a computer, or does a person buy a computer to perform a specific task or set of tasks? Back in '92, I knew what I wanted a computer for: BBSing, word processing, spreadsheet, programming, faxing, and helping me with my taxes. My 1MB stock A500 had a lot of trouble with a faxmodem; a 640k '286 could send and receive faxes easily. I had trouble finding software to help me with my taxes on my A500 (Canadian taxes), while some great software for doing my taxes was a free download away for even an ancient PC XT with an 8088 and single disk drive.
As for me, I held on to my A500 as long as I possibly could. I did eventually add a hard disk drive to help things along. To address my faxmodem and tax needs, I built a cheap junky '286 system for $100, which was cheaper than the used hard disk drive for my A500. I started out using it just for that, then I got hooked on using Telix for BBSing (which blew away JRComm and Terminus on the Amiga) along with the blueMail offline mail reader (much tighter and more feature-rich than Q-Blue on the Amiga). Next it was Lotus 1-2-3 for spreadsheets (mostly doing my budget), then I got a hold of a graphical version of WordPerfect for DOS. I wasn't playing many games (I felt I had grown out of that stage). My poor A500 was getting neglected; the bad and nasty PC invaded our home and took over.
It was a bitter pill to swallow. I take solace in the fact that I kept my original A500 all these years, while that PC has long since been sold. To me, the PC has always been a tool to do the job, and the Amiga was always something special; a future that could have been. I definitely hold the A1200 in higher regard than an old PC.
Now, because I don't really like talking about PCs, I will bow out of this conversation and go back to the original topic.
I felt this was more about the reasons why things went downhill for Commodore at around the time the A1200 came to market, and am sorry you have decided to leave. While heartbreaking, it's also an interesting topic for me.