He was no Spike Spiegel at all to me. That character (all of them really) was very clearly developed and Cho hit very few of the marks. Spike's a super laid back, disinterested, slacker... unless it's about Julia or Vicious, you don't really get a rise out of him.
I don't think Cho was unwatchable, but it wasn't Spike.
Vicious though, that dude was pretty much unwatchable. So terrible.
Jet and Faye by contrast, were almost spot-on personality wise.