Lengthy setup, but everything works fine after that

I installed the HP L7590 in January 2008, and I thought I would add my experience and advice to the other views expressed here.

First, please understand that we are using the machine on a small LAN which has both wired and wireless PCs, all running Windows XP. So I cannot comment on Vista or Linux, or Mac.

Second, my strong recommendation to any new user is to IGNORE the CD-ROM that came inside the box, since it has a version number which seems older than the driver software available at the HP web site.
Locate the up-to-date software [version 8.0.2, September 2008] online at HP.com, and download that 311-megabyte file to your hard drive or a USB drive.

Third, prepare an entire French Press of fresh coffee. Fourth, examine the brief setup instructions inside the box, and re-read them twice to make sure that you have not missed any step. On the third reading, I found two more strips of shipping tape on or inside the unit that I had somehow missed.

You should allow at least half an hour for the mechanical steps -- unpacking, plugging in to power and the LAN, installing the printheads and installing all 4 ink cartridges.
Choose a good location for the machine. Specifically, make sure that you have adequate clearance to lift up the cover all the way, and adequate clearance to pull out the tray that catches the paper. Assume that you will eventually use legal size as well as regular size paper. At first, I placed it too close to a door, and the first person who tried to close the door would have snapped off the output tray.

Go get a sticky label and write these words in some brightly colored ink: "Do not put ANYTHING on top of this machine". Make a couple of those labels and put them on and near the machine. The first person who puts a heavy book on top will destroy the feed tray.

OK, now just when you think it is all done pumping the ink and making noises, you are probably making the wrong assumption. Do not push any buttons at that time. Go make a few phone calls, and have another cup of coffee.

Fifth, choose any PC on the LAN that won't be in use for an hour or so. Use that PC to install the software that was downloaded. You should set aside at least 20-30 minutes for this step. Just when you think it is all done with the software installation and the printer has stopped making noises, you are probably making the wrong assumption. Do not push any buttons at that time. Go away and have another cup of coffee.

Sixth, come back and reboot the PC that you were using. Once you see the normal desktop, go away and chat with someone for a few minutes. Assume that some invisible but vital installation work is taking place on the PC. After you return, if all is quiet on the PC and the printer, reboot again to be sure.

Then click on Start > HP > HP Update and let it update whatever seems necessary. Once that is done, get another cup of coffee and reboot. Now, you should have an new icon in the system tray, called "HP digital imaging monitor"; if you double click on that, it will open the "HP Solution Center", which is the software that provides access to scanning, faxing, OCR, and printing functions. The bottom left button within the Solution Center is marked "Settings" and that is where you may go to mess around with the defaults. Personally, I thought it was easiest to set everything up by using that software, rather than pushing lots of buttons to go through lots of menus on the control panel of the L7590. However, if you are familiar with those menus from your old HP AIO, those buttons work just fine.

Seventh, you have had enough coffee, really. Try to be patient. Go to the second PC on your LAN, and repeat everything you did before to install the software and get HP Solution Center going on that computer.

Overall, the machine has handled everything that we have asked it to do so far. including printing, scanning, faxing (inbound and outbound), and copying in B&W and color.   We have left in on the "low quality" copy setting to save ink, but I must say that the quality has been fine. 
There may be functions I have not tried yet, but all the important ones have been exercised.

The is unexpectedly noisy when printing but silent in between jobs. It works fast enough for our small office, and I predict that we will see some decline in use of the old Laserjet 4 that is still on the LAN.

Unfortunately, plastic has replaced metal on most products these days. So I handle the equipment accordingly, and hope that by avoiding rough use I may delay breaking something. Like many others, I really do long for the good old days of well-designed and well-built machines. My LJ4 is made mostly from metal parts, but even the plastic parts are reasonably sturdy. Only the toner cartridges have been replaced, as needed, and it works just as well today as it did ten years ago.

After reading the other reviews here, and reflecting on my experience with the HP L7590, I DO recommend this printer. I expect that if it is installed with patience and handled with care, it will be fine for almost any small office. Of course, Your Mileage May Vary.
I have also concluded that the manufacturing quality control for this unit must be extremely uneven, and that is putting it mildly.  There are many negative reviews of this printer at other websites, but about twice as many positive reviews.