I did a lot of research, reading and talking to people before finally deciding on the Alen T300.  I was worried about a few things:
1.Noise
2.Filter service and price
3.Ozone generation
4.power consumption. 
I'm happy that this air filter really met all the criteria I was after.  Here's the breakdown...

  1. Noise.  Really what good is an air purifier if you cant sleep with the thing on?  Or hear the TV for that matter?  This air purifer is really quiet.  The white noise it provides at night when all is silent is equivalent to the sound of a hotel air conditioner running.  My wife and I find it quite relaxing and its nice to sleep along to.
 
  2. Filter.  The filter has a foam pre-filter that is easily removable and washable so the filters should last a long time, when they need to be replaced they cost $49. a pair (it uses two at a time) Not bad seeing that most people can get two years out of the filters running about 2200 hours a year. The UV bulb that can be turned on and off to kill  Virus and bacteria in the air can be easily replaced.

  3. Ozone- Read the EPA report people, Ozone is bad for your lungs!!! Many ionizing air purifiers produce Ozone (not good) the Inizer with the T300 is a negative ionizer (negative ions = good for humans, Positive Ions = bad for humans) so it doesnt produce ozone and its not harmful to humans.  If you dont like the idea of an ionizer at all you can simply turn it off.

  4. Power consumption- The power consumption over the past three months with two of these running on the #2 fan speed (low is 1, high is 4) for approx. 9 hours a day hasnt added much to our bill at all, actually its hardly noticeable that there even was a change in consumption of electricity.

  Fit and finish is top notch, and the controls are clear and easy to use.  All settings are clearly laid out for you when the unit is running so you know with a glance at the LCD screen whats on. 
  If your considering an air purifier, the T300 should be at the top of your list.  I purchased my units brand new for a cost of $270.00 each and best of all Alen offers a lifetime warranty on their products, because as they state "We dont want our products to wind up taking up space in a landfill somewhere".  Sounds pretty environmentally responsible to me.
  Go ahead, try one. I dont think you'll be disappointed with this unit.

Recommended: Yes

Amount Paid (US$): 270.
Battery Life: N/A
Noise Level: More quiet than most