I have noted that almost all the american made incandescent lamps that described as krypton filled lamps, have just a regular pear shape instead of the mushroom shape that accepted in Europe.
They also have usually too much life as krypton filling can be offer (>8,000 hours instead of 1 year or ~2,000 hours of the european krypton filled mushroom lamps).
The reason for the mushroom shape of the krypton filled incandescent lamps in Europe, beside decoration as they promoted initially, is mainly to reduce the required volume of this expensive gas. This gas offers 10% more light and 50% more life then argon (http://www.lamptech.co.uk/Documents/IN%20Gases.htm).
So, are the american pear shaped lamps that described as krypton are really krypton filled lamps, or that they are a deceit, and these lamps actually argon or nitrogen filled and are actually severally underdriven?
Picture of a GE hungary 230V 60W typical european krypton filled incandescent lamp can be seen here: http://www.lighting-gallery.net/gallery/displayimage.php?pos=-41796 .

For sure 8000hour rated krypton are running at lower temperature, so efficacy, then normal argon/nitrogen 750 hour lamps.
But in US are offered "energy saver's", that are krypton filled, so for 750hour rating offer ~10..15% lower consumption for the same lumens then standard lamps.

In Europe krypton filled bulbs are offered with the same wattage (40, 60, 75W), but with increased lumen output.

In my eyes keeping lumens and reducing the wattage is better way.

The A shaped long life krypton bulbs indeed do have krypton but are pretty expensive lamps costing around $1-3 per bulb. Even with krypton they are still inefficient due to their extra long life and vibration resistant construction. In the 70s and early 80s Westinghouse marketed a popular krypton bulb called the Superbulb, it had a reduced outer bulb envelope to lower bulb costs. It had a coiled coil filament, full wattage, and 3000 hour life. Despite the rated life, gas allowed the bulbs to be nearly as bright as their 750-1000 hour counterparts. I have about 4 Superbulbs in my collection (3 100w and one 60w).

@Medved: Thanks. However i don't think that all of the "Energy saver" incandescent lamps in the US are actually krypton filled. Several have just a lower wattage in an argon/nitrogen atmosphere and a lower lumens respectively.
Dave, in Israel, krypton filled incandescent lamps costed slightly less higher then the american ones (I think around 10 NIS for 60W lamp, but i haven't sure, still they weren't so expensive i think), perhaps because of their mushroom shape. They offered only in white finish to add to their decoration. Their still rated 1,000 hours life but the actual life is 1 year average or 3000 hours max indeed. They also produced 10% more light. Osram Gmbh called these lamps Superlux Krypton.
Reduced size (Not krypton filled) incandescent lamps we had also, but they have shorter life because the glass operates at higher temperaure. The reduced outerbulb in the case of the Westinghouse Superbulb is as an alternative to the mushroom shape of the european krypton filled lamps (Also a way to reduce the required volume of the krypton) and therefore there was no loss in life.

Hi dor123, here is my specimen that is Duro-Lite Watt Saver 92W Light Bulb that is posted on this site and I thought you might be interested in the variety of American bulb that are filled with Krypton gas.

As you can see not much of change of the lighting output and life of the bulb itself.  But the price was just pretty much above the par of the cost of the bulb itself in the late 1970's USA price listed on the package.  I can still remember the day I bought the bulb at Montgomery Ward at Randhurst Shopping Center, Mount Prospect, IL, USA.  It seems ages ago

But there were other wattage sitting on the shelf also sold as 135 Watts version (If I recalled correctly) as well.