Don't get too excited, Dave… no drivers have been released for onboard sound or ethernet so far as I know. What I have done is the admittedly radical move of removing the ethernet card and, thus, Internet access. (I can confirm the onboard ethernet port does work in Debian.)
I doubt anybody else will want to do this, as everybody goes on and on about web browsers and such. But in my case I certainly have lots of computers to get online with, including more than one at the same desk where my X1000 is installed. What I want this machine for mostly is running new and classic Amiga creative applications. You see, I remember the pre-Internet period when I was most productive with my Amigas. These days I surely do waste a lot of time on, ahem, Internet forums and such. I mean, I could be reading threads about how useless an X1000 is or I could be using my X1000 to do something useful. That's the way the view looks from here anyway.
I expect we'll have drivers for the onboard ethernet and sound sooner rather than later. No inside knowledge, and maybe that's just wishful thinking.
Obviously the ATI 9250 card works, as I've used it with both a Sam440 and now the X1000. (I'm keeping my little Sam440 with the onboard M9 video but likely will sell or keep as a spare my Sam440ep-flex motherboard that had the 9250 card).
I have no experience with other cards. I have a spare 9200 card in a PowerMac G5 PCI slot, but I haven't tried it and suspect it's a Mac version that would have to be re-flashed or whatever the term is. I'm not going to bother with that.