Hi Chuck,
In a tracker, you don't have to write in 4/4-- you can freely change the lengths of each pattern and even cut patterns short with a simple command. How intuitive this is depends on both the user and the program. Also, notes are not all the same length. Rather, a note in a tracker turns a note on. If you have no sustain on that instrument, then yes they will all be the same length (as in a sequencer). Notes are also not necessarily quantized, as every good tracker has commands to delay and stop notes on ticks and not rows. Furthermore, many good musicians that use trackers increase the speed so that every row is a 32nd note and not a 16th note.
As to the comment that you can only produce "retarded dance music" with a tracker, I will say this: while trackers are designed for styles of music with repeating sections (whether it's a dance track or simply verse/chorus/verse/etc), you can do a wide range of styles with them. Judging the tools by the majority of music created with them would maybe lead someone to also believe that Cubase is also incapable of anything but dance music, right? =)
Hope this helps! Trackers are very complex and are often misunderstood as the aim is slightly different from that of a sequencer.
Long time tracker (since '92),
Louis Gorenfeld
