Product review (5 stars): works well
I have a Honeywell HE365A humidifier, and this pad fits perfectly.  I cranked up the humidifier, and the house went from dry air to too humid (75%), so I turned it down a bit and it's now perfect.  Tip -- buy a hygrometer to check humidity; I got one by Acu Rite at my local hardware store for $4 and it also has a thermometer.  I like that the pad has an antimicrobial coating, since humdifiers can cause health problems if micro-organisms grow in them (problems mostly happen in humidifiers that have water tanks; the HE365 & HE360 don't have water tanks).

One reviewer complained that the humidifier was leaking.  Check that your drain hose is not clogged.