You might want to search around over at
http://avsforum.com.
There is a ton of info over there. The newer sets (87's and 88's) are getting a TON of discussion.
I just upgraded from a panasonic 50" DLP to a 56" sammy DLP 1080p. I'm probably jumping the gun a bit, but the 87 series in particular are getting pretty cheap since the 88's came out. The 88's have cablecard (1.0), QAM tuner and PIP, but are otherwise pretty much identical to the 87's. Since I use an HD Cable DVR, I don't really need any of those things.
My father and sister both have 42" 86's and they both love them, of course they both upgraded from 27" CRT's, so they were easily impressed.
I helped them get set up. They suffer from the same problem most all of the samsung DLP's suffer from. They are awesome display's but out of the box the picture is way too hot (bright).
Over at avsforum, one of the pro calibrators (Eliab) posted a good set of user settings for these sets (to use as a starting point).
http://www.avsforum.com/avs-vb/showthre ... ost7929165
Eliab wrote:Digital NR - OFF
DNIe - Off
Mode - Movie
Contrast - 40
Brightness - 45
Sharpness - 0
Color - 45
Tint - G50/R50
Color Tone - Warm2
This thread is on the 87 series, but I used the same settings for my fathers 4266 and it looks great.
Honestly though if you want the most out of these displays, you'll probably want to include the cost of professional calibration. These are usually done after 100 hours or so. Everyone who has had this done raves about these sets. Off the street price for a full service menu calibration runs around $400-$600 depending on how thorough they are and what kind of equipment they use.
You can get the service menu remote codes off of the forums, but I've looked at mine, and there is no way you can do this yourself. And there is no reset to default function, so if you screw something up in the service menu, you will end up paying for a service call. Not only that, to properly calibrate you really need a light meter and colorimiter (which isn't cheap), and know how to use them.
Edit:
Here is the Samsung 720p HL-S owners thread.
http://www.avsforum.com/avs-vb/showthread.php?t=671006
It's only 27 pages. The 87/88 series threads are all over 500 pages now. The number of posts per day on that site blows me away!.
Edit2:
Something to think about. The one comment I hear quite a bit is that you really start to see the benefit of 1080p (over 720p) when you get into the displays of 60" and up. The extra resolution apparently really makes a difference.
Edit3: I just re-read your post. I would give some serious thought to spending that kind of money on a set that big if you are primarily looking at SD sources. This is the one area these sets are a bit weak in, especially the bigger ones. If you are going from a smaller CRT to basically the equivalent of a 50" CRT, but still basically viewing the same number of horizontal lines (480). They can get really grainy, especially at the bigger sized. Id definitely try to spend some time watching them with this type of source connected (standard DVD, or SD Cable) before you buy. I'd also recommend you buy somewhere you can return it (and get service calls made) in case you run into trouble. The cheaper places online (i.e. amazon.com) won't let you send any set over 27" back to them once you've accepted delivery. You'll be stuck with Warranty calls. Quite a few people are shelling out cash for extended warranties because of this (I did not).