Even the A500 was not compatible with certain software after you expanded the memory or updated the Kickstart Rom. It was a simple fact of the changes made to the way libraries were loaded as well as enhancements that were done broke programs that were hard coded to work a specific way. To bypass this issue there is a wonderful program called WHDLoad. You have to have licensed and legitimate images of the various kickstart ROMs (buy Cloanto's Amiga Forever software.) and you use this program with extended memory to load and play programs that aren't compatible and from the hard drive. Now an A500, or A600 will never be able to play AGA games, but considering that the number of those games is quite small, it isn't too much of an issue. But it definitely is better to have Kickstart 3.1 and at least Workbench 3.1. Compared to previous versions this release was extremely stable. OS3.5 and 3.9 are really for expanded 1200's and Desktop 4000's really, so I wouldn't recommend purchasing either one of those.
Also check out a cool 3.1 desktop update called ClassicWB. It sets up very nice graphics and comes preloaded with some great tools. If I knew how to load video I would do a video of my A600 with it so you could see what it looks like, but I haven't ever done that before.
Even the A500 was not compatible with certain software after you expanded the memory or updated the Kickstart Rom. It was a simple fact of the changes made to the way libraries were loaded as well as enhancements that were done broke programs that were hard coded to work a specific way. To bypass this issue there is a wonderful program called WHDLoad. You have to have licensed and legitimate images of the various kickstart ROMs (buy Cloanto's Amiga Forever software.) and you use this program with extended memory to load and play programs that aren't compatible and from the hard drive. Now an A500, or A600 will never be able to play AGA games, but considering that the number of those games is quite small, it isn't too much of an issue. But it definitely is better to have Kickstart 3.1 and at least Workbench 3.1. Compared to previous versions this release was extremely stable. OS3.5 and 3.9 are really for expanded 1200's and Desktop 4000's really, so I wouldn't recommend purchasing either one of those.
Also check out a cool 3.1 desktop update called ClassicWB. It sets up very nice graphics and comes preloaded with some great tools. If I knew how to load video I would do a video of my A600 with it so you could see what it looks like, but I haven't ever done that before.