Hey,
on ubuntu, I have good experience with:
-echo layla 3g (8in8out,2preamps, phantom...)
-m-audio delta 1010LT
-m-audio delta 44
-rme hammerfall dsp + multiface, both PCI and PCMCIA (note: the output jack sockets are too close to each other, which can give you a hard time connecting more than 2 cables with 'sturdy' jacks.)
all those worked pretty much out of the box
bad experience with:
-firewire soundcard using 'freebob' driver
(I think the brand was motu, or presonus, or focusrite, one of those, I don't remember exactly...but, while it was officially supposed to work (checked alsa soundcard matrix) it didn't...)
I haven't checked recently, but I still have the impression that firewire soundcards are poorly supported on linux...