The expandability of the original Amiga platform is what kept the ecosystem so vibrant that there almost wasn't a need to update the platform for so long - so many expansions that the Mac people could only dream about. Video Toaster, to name but one. I started with an A1000 that I hacked a 20MB hard drive into, along with the usual RAM expansions. I moved on to a fully-loaded A2000 system with a 68030 CPU, 1GB of hard drive space, 64MB of RAM, ethernet card (coax), an Apple Mac emulator card, a PC card that ran PC software on the card, a PBX card to hook up to interface with the phone line, and just so much more - while the Mac was still pushing black and white graphics and 512KB RAM (and very, very difficult to expand the RAM).
I later got an A1200, and then an A4000 as well. While the platform updates were great, those weren't what really made the Amiga shine - it was the multitasking OS that the Mac and PC didn't really have - they were nowhere near Amiga OS, which was pretty amazing. Through AREXX any application could control any other application, which is something Windows and OSX still don't really do. I mean to some extent it's sort of possible now, but not as easily as it was with Amiga OS.
If Commodore was still around and had not gone out of business, I'd absolutely be using Amigas today. (yes, I know it sort of still exists, but it isn't really funded or widely used)