Here is some information on the Eclipse AVN 5510 installation I have done in my wife's 2000 ES300 - everything works as advertised, so far it's great.
Looks like it could easily be OEM, the illumination color on the panel buttons match the climate control buttons. The iPod control interface is really nice too. Items with part numbers that I used in this install:
- Eclipse AVN 5510
- Eclipse Eclipse iPC-106 (iPod Control Interface for Eclipse iPod Ready Stereos)
- Scosche LS2081B (Double DIN Installation Kit for Select 1997-2003 Lexus ES300)
- Metra 70-8113 (LEXUS ES300 1999-2001 AMP BY-PASS)

Added the following items (from Crutchfield):
- PAC SNI-1 RCA Ground Loop Noise Isolator (x2) - these helped only a little
- American International S15A 15-amp/250-watt Noise Filter - eliminated 90% of the audio buzz
- American International AS100 Noise Filter for Motorola Antenna
- 1 day subscription here for splice locations for Vehicle speed sensor wire, parking brake wire: https://techinfo.toyota.com

Installation was not too difficult.
It's a tight fit as there is a HUGE pile of wires that go behind the system along with the noise filters. The VSS and parking brake wires were tough for me to get to, may be easier with the drivers seat removed. I am going to reroute the parking brake wire to ground - so playlist controls and navigation changes are available while the car is moving.
Here is a picture:

 

That looks real clean and nice. Job well done. Do you have any issues with glare?

 

Not so far - my wife's been using it daily since last July and hasn't mentioned any glare issues.

However, I do not have the illumination wire connected and the display is WAY too bright at night, even when dimmed down all the way. The display inverts to white roads on a black background in night mode vs. colored roads on a white background. Here's the daytime mode:

 

very very nice. clean install buddy. how much did the whole package set u back?

 

Grand total back in July '07 was about $1200.
Now I see that the 5510's are on sale for $899 w/ipod adapter free, so the whole setup would be less than $1K today.
It's been worth every penny - no more calls for directions from my wife + she no longer has to print out maps w/directions, and the ipod integration is excellent.

$1095 - Eclipse AVN 5510
$49 - Eclipse Eclipse iPC-106
Free - Scosche LS2081B
$8 - Metra 70-8113 (LEXUS ES300 1999-2001 AMP BY-PASS)

About $70 for the other items:
- PAC SNI-1 RCA Ground Loop Noise Isolator (x2)
- American International AS100 Noise Filter for Motorola Antenna
- 1 day subscription here for splice locations for Vehicle speed sensor wire, parking brake wire:

 

Is the Scosche LS2081B the best kit for those ES years? Love how flush it looks In there

 

Did you custom make the plate for the GPS System? I really want to install something like this and have it looking clean.
- Ishaan Mistry