This is a little long winded so apologies in advance.
HLS5087 owner since October and have been pleased with it for the most part. 3 issues for me are:
1) SSE (note tv is at foot of bed so viewing distance is pretty close at 83").
2) Flesh tones weren't always accurate and just a general nagging feeling regarding the overall picture quality of "Is that all there is?"
3) Geometry (primarily with 4:3 material, sometimes notice bowing in vertical lines such as doors, etc) I wish Samsung would offer a low gain screen as an option.
Signal sources are Comcast cable via SA 8300DVR & Toshiba A2 HD DVD (both connected via HDMI).
Calibration doesn't really address items 1 & 3. Using Eliab's settings, the picture was already pretty good and sometimes great, but item 2 bugged me like a low grade headache. I was a little skeptical, but decided to go for it anyway.
UMR calibrated a couple of nights ago and I'm happy as a clam. Specific improvements included more natural fleshtones, better color saturation in some instances & more shadow detail. Many scenes (check out the munchkin scene in the "Wizard of Oz") jumped from being three to THREE dimensional. I'm not a video geek and not into all of the analyticals. I'm more of a threshhold guy in the sense that pre-calibration I was a little under the bar of being happy with the set. The cumulative effect of the calibration improvements puts me over the bar with clearance.
Is a professional calibration necessary? It's a struggle to not oversell / undersell the benefits. It's not a night and day difference. It's more like the improvement in a car's appearance after it's detailed, a meal prepared by a good cook rather than an average one, finding the perfect outfit rather than settling for something close, etc. The above have in common the fact that a given individual's interest could range from very high to zero.
So, the answer in my opinion is "No" for the vast majority of folks who "just" want to buy a set at a reasonable price with a good picture and watch tv / movies. But, for those whose interest is more towards the "high" part of the range regarding their set's picture, a pro calibration (& UMR in particular) is highly recommended. It takes you up to the next level which is a good thing (would also put a high def and / or good upscaling DVD player into that category as well).