Echo Indigo is pretty good. Thus far have not hade any compatibility (with music/sound software) issues. ASIO works well. There is nothing fancy like game support (EAX stuff) or multi-channel (5.1) in it. It's purely for stereo output/recording.
I like manual volume control on the card. Have not recorded much with it - I primarily use TonePort UX1 to record guitar - but it worked well for mixing in Sony Vegas 7 and with ACID Pro 6. I also enjoy listening to music through it.
Keep in mind that AFAIK there is no Vista driver for it.
With PCMCIA slots going away (replaced by ExpressCard), a better investment for a long-term would be to get external USB2 device (M-Audio, Line 6, ...) or Firewire (Echo, M-Audio, PreSonus,...). This seems to be the trend lately.