I like them but not my favorite. To me the 7550 are more neutral than the W4 but lacks the instrument separation the W4 possess. W4 also has better/more forward mids. I really liked the FX700's but the bulky housing ruined the fit for me. The 7550's are way more mellow and less sparkly and bass hits softer going from memory. My favorite universals have been the JVC FXD series since they've come out. The FXD80's are something else. It's more colored then the 7550 but does it in a good way. Plenty of detail but adds a fun factor I can't resist.
The FXD80 and the 7550 both seem very typical of their respective categories; consumer and professional monitor. They both have their appeal :3 I'm sure that eventually JVC will put out a reference version of the carbon nanotube design though, which might be the best of both worlds.