I'm not familiar with many 'plug-in' LED fixtures.
White LEDs are still relatively new. In the past few years the efficiency has increased to the point where LEDs are now slightly more efficient than most fluorescent fixtures. CREE semiconductors latest white LED offerings (xlamp, xre) are of a higher caliber than the older 5mm LEDs. These white LEDs have a lifespan of over 50,000 hours and in the best cases you get a clean, elegant white light.
(cree's site) link
(seoul semiconductor) link
To get a white light these LEDs combine a blue LED with a scintillator (like a phosphor) which creates the rest of the spectrum (green thru red). The problem is variances between each batch of LEDs and the scintillator used means the tint of each LED is a little different. Because of these tint variances each LED is graded, or 'bined'. Higher grade LEDs will have the purest white and they are also the most efficient (create the most light for a given amount of power). Cheap, poor quality white LEDs often have hideous tints (purple, green, blue) which make them unsuitable for indoor lighting, IMO.
These new LEDs create of lot light from a very small package - the die is just a few mm per side. You might get over 100 lumens from one of these LEDs. This isn't bad - a hundred watt incandescent light bulb puts out 1800-2000 lumens for comparison. So to get a lot of light from an indoor fixture you're going to need multiple LEDs. You also want a decent current regulating power supply. Some power supplies used in flashlights use PWM which means the light flickers at high frequecies.
It's still cheaper to use CFLs, fluorescents and high wattage discharge bulbs if you need a lot of light indoors... however I'd expect to see an increasing number of LEDs for mainstream use in the next 10 years. Once the quality of the light is improved, along with increased efficiencies, and LEDs may well come to dominate all lighting.
However there's one area these new LEDs really shine in. Flashlights. The benefits of the LED - very efficient (long run times), tough, small size & long life. These newer LED flashlights should be part of any bugout/survival kit.
Here are the three premium LED lights I own: (800x600 pic) jpg
All of these lights use the new Cree xre/xlamp LEDs. From left to right, the Fenix L2D, Fenix L1D, cr2 ion.
The L2D runs off 2 AA batteries. It has several brightness levels. The low setting (around 10 lumens) lasts for over 55 hours! (over two days). These lights are regulated to supply a constant level of light until the batteries are nearly dead. The low setting supplies enough light to read, navigate and do most chores up close. The L1D lasts over 25 hours on low, and ion is close to 35 hours of light on its low setting. Combine these with rechargeable batteries and a solar charger and you'll always have light. I've been using the L2D as a lamp on my computer desk for the past year. I set to its medium setting (around 50 lumens for 9 hours) and stand it on end pointing towards the ceiling.
You can get these lights here: link
My recommendation is to stick with the new Cree and Seoul (which uses the cree die) white LEDs - these are a big step up over previous generations, especially 5 mm LEDs. They should last nearly forever.
Comparison of Cree and Luxeon Rebel LEDs. The cree (on the leftm L2D) has a cooler, bluer white, compared to the warmer tinted Luxon (in the L1D): jpg
Few more pics. Close up of the ion finger light: link
On low the ion has a runtime of well over 30 hours. The lithium primary battery has a 10 year shelf life and works in weather extremes (including cold) that would kill an alkaline battery. It supplies enough light to navigate a dark trail or read a book, and the output is very smooth (flood) with no annoying hotspot - perfect for up close work. In the image below I'm using it as a reading light suspended about 20" above the books (low setting): link
If you are looking for more information on LEDs, try the candlepower forums: link