If the Apple TV noise bothers you then you will have issue with the mini. ATV doesn't even have a fan. The only thing you could be hearing is the hard drive.
I started thinking about Intel shrinking things and the associated power drop and wondered what Apple might use as a next processor, so I made up this below. Do current MB's run cooler than the ones a year ago (when I got mine).
Current Mobile Processors
Merom, 65 nm, standard voltage
Core 2 Duo T5200 1600 MHz Oct-2006 34 W
Core 2 Duo T5500 1667 MHz 28-Aug-2006 34 W
Core 2 Duo T5600 1833 MHz 28-Aug-2006 34 W <--- current Mini
Core 2 Duo T7200 2000 MHz 28-Aug-2006 34 W <--- current Mini
Core 2 Duo T7300 2000 MHz 09-May-2007 35 W
Core 2 Duo T7400 2166 MHz 28-Aug-2006 34 W
Core 2 Duo T7500 2200 MHz 09-May-2007 35 W
Core 2 Duo T7600 2333 MHz 28-Aug-2006 34 W
Core 2 Duo T7700 2400 MHz 09-May-2007 35 W
Core 2 Duo T7800 2600 MHz 02-Sep-2007 35 W
Merom, 65 nm, low voltage
Core 2 Duo LV L7200 1333 MHz Q1 2007 17 W
Core 2 Duo LV L7300 1400 MHz May 2007 17 W
Core 2 Duo LV L7400 1500 MHz Q1 2007 17 W
Core 2 Duo LV L7500 1600 MHz May 2007 17 W
Core 2 Duo LV L7700 1800 MHz 02-Sep-2007 17 W
Merom-2M, 65 nm, ultra low voltage
Core 2 Duo ULV L7500 1066 MHz 05-Apr-2007 17 W
Core 2 Duo ULV L7600 1200 MHz 05-Apr-2007 17 W
Core 2 Duo ULV L7700 1333 MHz 30-Dec-2007 17 W
Penryn-3M, 45 nm, standard voltage
Core 2 Duo T7350 2000 MHz mid 2008 17 W
Core 2 Duo T8100 2100 MHz 06-Jan-2008 17 W <--- current MB
Core 2 Duo T8300 2400 MHz 06-Jan-2008 17 W <--- current MB
Penryn, 45 nm, standard voltage
Core 2 Duo T9300 2500 MHz 06-Jan-2008 35 W <--- current MBP
Core 2 Duo T9500 2600 MHz 06-Jan-2008 35 W <--- current MBP
Future Mobile Processors
Penryn-3M, 45 nm, medium voltage
Core 2 Duo P8700 2533 MHz Q1 2009 25 W
Core 2 Quad, 45 nm, standard voltage (expected initial cost $800)
Core 2 Quad Q9100 2266 MHz Q4 2008 35 W
Nehalem, 32 nm, ??? voltage (power optimized)
Core 2 Quad Q9100 ???? MHz Q3 2009 35 W first mobile Nehalem
(future MBP)