High output CFLs make the old pendant lamps practical for use as area lighting. These replaced 175w MVs and only use 68 watts of power to provide the light equal to a 300w incandescent bulb. The color temperature of the CFLs makes the light produced a lot more "usable" for area lighting.
Actually base up, but Devonte is right. If it's in an enclosed fixture, the heat will build up. And with the electronics above the lamp, they will virtually cook inside the CFL ballast case. Thet can even catch on fire! As long as you use a good quality CFL, you'll be fine.
Going on year 5 with the CFLs with no failures. Not saying that the concerns expressed about the electronics packages and heat aren't absolutely valid. From my experience and checking around the 68 watt CFLs seem to do fine in full NEMA size fixtures with adequate air space (full size gumballs or teardrops.) I have read reports of the higher output kits having heat related failures when placed base-up in dusk to dawn operation. 4,200 lumens seems to be adequate so I'll stick with this size.
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As long as you use a good quality CFL, you'll be fine.