Summary: I bought the T100 back in 2008 for my son who has dust allergies. It's worked well, and using a Kill-A-Watt, I found that leaving it on 24/7 on low costs something like $1/month. Last week, the fan got pretty loud, sounded like it was loose or a bearing was shot. I took it apart to see if I could fix it, then couldn't find my graphite powder and decided to check the warranty on Alen's website. Lifetime?? No way.
Summary: I've been using this air purifier in my room for several years and it's still working fine. It is very quiet at the lowest fan setting. Even at the highest setting, it is not as loud compared to the other air purifiers being sold in the market. I mostly use it at night time and could tell the difference when it is not used in the room.
Summary: First of all I did not expect any magic out of this device in first place. I bought it to have additional air cleaning in kid's room. I have no objective mechanisms of measuring if it really improves air quality or not. Subjectively I find air in the room more pleasant to breathe when this thing is running so does my family.
Summary: I've owned A LOT of air purifiers because I suffer from chronic sinusitis. This unit is simple to operate, seems very well made, is extremely quiet (even on high) and leaves a "fresh" smell in my laundry/utility room. I purchased the optional odor absorbing filters. My only complaint there is the price ($89 for a two-filter pack).
Summary: I have Alen T300. It is whisper quiet unit with good performance. I wanted to buy smaller unit for bedroom and ordered T100 expecting it to be similar to T300. Only similarity between these two units though is design and HEPA filter - T300 uses two TF30 filters and T100 only one. T100 has also lower power consumption - 13Wt at low speed compared with 20Wt for T300. But it is louder - 39 db vs 36 db. Those 3 db make all the difference (3 db doubles audible sound level).
Summary: I can't give a complete product review because this was a present for my mother who is asthmatic. It got there in great time and so far it's only been a month but she loves it and has said that it's not loud or extremely big. So for the price and the other good reviews I feel that this was a good buy!