Excellent unit overall. I am very happy with it.

Navigation is simply outstanding. Very Accurate. Quick to reroute. My wife comments that 5510 is "smart". I probably asking too much but I wish Eclipse put the traffic feature in 5510.. (you can find this feature in 6610)

Audio: The built-in EQ and subwoofer signal controller is very good. Amp is rated as 15W RMS, which is not bad, but my front speakers are 100W RMS, so without external amp my speakers sound pretty distorted when I crank up the volume.

Video: Screen quality is good.

I installed the unit myself on my Lexus GS400. Crutchfield's instruction sheet is excellent. If you do the installation yourself, be sure to get a installation dash kit. Crutchfield also provides a harness for free. The Eclipse Operation Manual is not complete, but you can download the complete manual online, it's in PDF format.

I used to own a couple portable NAV units. This AVN5510 wins in a landslide, hands down, in terms of OEM look, feature-set, ease-to-use, everything.