These are essential parts of a home entertainment system to keep everything protected and in check.
The power conditioner will isolate your system from the effects of the outside world, provide surge protection and noise removal, Noise removal being the big thing. The less noise there is entering a system, the more efficient it will run, and thus produce less noise itself. This increases lifespan and improves on picture and sound significantly.
I would recommend Monster Power (although overpriced), as their HTS-series makes a real difference. Also, for those with more financial resources, RGPC (Richard Grays' Power Company) makes power conditioners from $750 and up. These are reference grade.
UPS (Uninterruptable Power Supply) is essential to the Northeast or anywhere that loses power for that matter. The more common application is with computer-based systems, but let's face it: most HT components are getting more and more to be like a computer. Combine that with the media center PC market and you've got a purpose. Furthermore, you can catch the tail-end of a game when the power goes out when nobody else could. This also prevents the loss of any settings. I would not buy an HDTV flat panel without one.
APC is excellent for battery backups. They never seem to overload with reasonable loads and have shown excellent reliability. Monster Power is good also, but not only is it overpriced, but it is nothing like an APC for 1/3 the price. RGPC comes in again as my top-end recommendation.
As for the comments on glare: Glare happens to every panel, glass, plastic or in between. It is simply the kind of glare one receives. Plasmas give reflections. Matte finish LCD's undergo the bleaching effect, where the picture washes out into an oblivion of pastellized color. As light exposure on a matte finish LCD increases, visibility decreases, not because of reflections, rather because blacks turn to grey, reds to pink, until finally one ends up looking at a bright grey screen. This matte finish is not desirable for 4-season rooms, for example (which explains why plasma is the top choice for rooms of that nature). Samsung LCD's use a glare-finish, which induce more reflections than a traditional round-tube TV, but do not bleach.
Sony and Sharp have been smart enough to implement a semi-gloss finish, which incorporates the advantages of a matte-finish screen and a glare screen (glossy). This combines the resistivity to reflections with less tendancy to bleach. For LCD's anyway, this is ideal for most conditions.
Plasma displays incorporate anti-glare coatings (many manufacturers, from Pioneer to LG, etc.) as well as screen filters (Pioneer). some plasmas (Panasonic TH-42PZ77U and others) seem to have a full-matte finish . These have been shown to have silkscreen effect, a glittery appearence, still with reflections. Also, loss in contrast in high lighting is huge. Only the Pioneer amoung plasmas has seemed to get it done right. They incorporate an 80% screen filter with a glossy anti-reflective chemical coating (no silkscreen!) to provide 100% available contrast in almost all lighting conditions.