i can speak up as someone who has avoided any interactions with the ALSA sequencer for years because of a similar perception. i recently converted Tim Thompson's KeyKit from its raw MIDI port-based implementation under Linux to one that uses the ALSA sequencer (and adding multiport support along the way). it was suprisingly easy and obvious, given a simple example (in this case, the "ALSA sequencer MIDI Port object" that someone contributed to Ardour). even more gratifying was comparing the code to the keykit implementations for win32 and CoreMidi. the ALSA sequencer one was smaller, more logical and less bogged down in details.