The HP LaserJet 3700 is a wonderful beastie, capable of generating colour laser printing pages at a rate of 16 pages per minute (ppm), regardless of whether it's black or white or colour. This makes it more expensive than its cheaper cousin, the HP LaserJet 2500; but essentially, they are the same technology. The 25xx series has a single applicator (which makes it smaller, but colour pages need to go around four times), whereas the 37xx series has the ability to apply all four colours in one pass.
As a result, colour pages churn out of the 3700 at a rate of 16 pages per minute, whereas on the 2500 black and white comes out at 16 pages per minute, with colour at 4 pages per minute.
The quality is excellent on the HP printer, and the support is superb. I have it installed on my Mac OS X network, and with Rendezvous (sorry, I mean OpenTalk) and it comes up automatically. I can even browse to the admin console in Safari's rendezvous bookmark.
The 37xx is aimed at workgroup printers, and as such, comes with a little more RAM and a faster processing speed than the 25xx, but it's a big beastie, and not the kind of thing you're going to fit in a small home office. The 25xx is probably a great compromise if you want HP's quality, but at a more affordable price and smaller footprint.
Both pictures and text come out really well; I've printed some A4-sized prints taken with a 3 megapixel camera, and even with vivid colour photos the print is very detailed. I suspect that the ImageRet 2400 is helping here, and if I had a more advanced camera I may even be able to see more detail.
What's nice (compared with other colour systems) is that the 37xx (and 25xx) have 4 separate colour toner cartridges, so if I print a lot of landscape photos with a blue background, I can just change the blue cartridge when it runs out. This is a massive improvement over InkJet printers that have a 3-colour cartidge that you have to throw away at the end of each print run.
It also does really well on printing black and white documents with colour pictures. When printing a mixed-content document on an InkJet, most of the time it mixes the 3 colours to create a black effect rather than using the black cartridge (though this is more likely to be because of the crappy Lexmark drivers). With the 3700, it uses the 4-colour (black, cyan, magenta, yellow) so black text comes out crisply in black. Again, good drivers are likely to be an advantage here; and whilst Macworld reviewed the 2500 as coming out slightly green, I think that was a driver issue with their setup since I can guarantee that an HTML document printed with crisp black text and colourful pages.
HP have also launched a 2550, which is a faster model than the 2500; being able to print at 19 pages per minute. I suspect that a 3750 may be somewhere in the future.
If you're looking to buy a colour laser printer, I can highly recommend the HP printers. They support most operating systems (Mac OS X drivers are included, for example) and the configuration is a cinch. I'd recommend the 2550 for size, price and speed over the 3700 (b&w is 19 versus 16, but colour is 4 versus 16) for a home location; unless you're using it for colour most of the time, in whcih case the 3700 wins. If the 3750 is released, I'd expect that to run at 19 pages per minute for both.
The main reason to buy the 3700 is that it is the cheapest and most flexible colour laser printer with duplex support (though only on the 3700dn and 3700dtn models). If you're printing a lot of pages and want to save paper, duplex is the way to go. But from a price-only point of view, you're going to have to print a whole lot of pages to make buying (and servicing) the duplex unit.