There has been a lot of discussion regarding navigation systems under AUDIO & ELECTRONICS. You will find a lot more info there.
There are so many factors & variables that will, or should determine which nav system you purchase. Obviously, price is a huge one. But other things to consider should be the functions you want on the unit, quality of display (and whether or not you want touch screen), navigation mapping detail, bluetooth & ipod ability, steering wheel controls, etc.
As far as the navigation goes, are you concerned about it being an all-in-one? Many units have nav built in, but offer less options & features. Others have external units, and therefore have more features built in.
The OEM Toyota navigation system is a good system. If you have the single indash radio, you will need to buy a different dash trim piece, as well as replace the air conditioning controls with one made for a 6-disc unit.
The aftermarket "OEM" company has stuff in Crutchfield, but I've never seen one in action.
Aftermarket units are generally sized by the industry standard as single Din, or double Din, and are smaller than the OEM opening. You can get aftermarket trim kits to fill in around the nav radio.
The unit I have installed is a Kenwood unit / system, with separate nav unit, etc and really like it. There are many things I wish it had or did, but overall, I am happy with it. Kenwood also makes several units that have nav built in.
The Alpine systems are very nice. I personally haven't seen the Blackbird in use, but the NVE-N872 is phenominal. But very cost probihitive. If I had the money, I would very possibly get this.
Clarion is another company with very good offerings. They don't have any units with built in nav though. So if that is what you are looking for, keep looking. If not, I think you will be very happy with Clarion. This was in close running when I was shopping for a unit. Excellent features and detail.
I've owned Pioneer head units and equipment in the past, but I've never owned a Pioneer nav unit. For more Pioneer info you may want to check out the website AVIC411 (or something like that). Do a google search.
From what I understand, Eclipse is a direct plug in for some Toyotas. I can't remember if it is the JBL, or non-JBL. Remember though, that Eclipse doesn't offer anything for Bluetooth except for a Parrot kit.
Just remember that everyone is going to have different opinions about each one. What one person may like, another may think is a piece of crap. Make a list of what you want in a unit, do your homework, and research each one. Crutchfield, and each prospective brand will have info on their websites.
Ultimately, you are the one paying for it. It's in your best interest to pick the one you like - not the most popular one, or the one everybody else likes.