Write your own HTTP API wrapper that throws exceptions — come on, you’re a programmer, do what programmers do: make a personal, convoluted abstraction layer. :-)
Andrew Nacin on WP_Error
Which is a nice read on wp-hackers by the way, about how WP_Error is used and why it shouldn’t be replaced by PHP5 exceptions, which I never liked. If you’re really thinking of writing an HTTP API wrapper, please don’t :)
Interesting discussion.