I have very good initial impressions of this unit after installation. I'll update this review after a month or so of heating season which begins very shortly.I bought this unit to replace an approximately 10 year unit that had smaller dual 18 watt bulbs. The second ballast that the unit had very recently failed. The first had failed more than a year ago so the unit was now non functional. I had first attempted to find repair parts to replace or upgrade the ballasts in my existing unit. However I found the cost was prohibitive in comparison to this brand new unit that also came with a new warranty and with higher output 36 watt bulbs.Install was mostly smooth even though the spacing I have to mount the unit above the air conditioning coil is very tight. There are water pipes from a water heater very close, and a small copper line for a humidifier which makes it challenging to maneuver the unit in and out. The unit is also placed just below a drop ceiling.The provided alignment guide was adequate to show me where I needed to drill holes for mounting and what additional sheet metal needed to be cut to allow for bulb clearance. I already had an existing hole cut in the ductwork where the previous unit was mounted. I simply reused this and widened as needed with some tin snips to accommodate the new bulb alignment.The dual external LEDs which show the operational status of the bulbs are very bright in a dark room and easy to see and very useful to confirm operation. The unit I replaced only had a sight glass externally to show you operation status, but could not tell you at a glance if you had a bulb burned out. This unit also has an external replaceable fuse, and a spare included. The unit I replaced was not fused.Installation did not take very long. The unit seated and sealed up very well against the air duct. After install and initial activation I temporarily put a piece of electrical tape over the status LEDs. With the room dark I applied some metal tape to a few seams in the sheet metal that you could see small amounts of diffused UV light leaking from. The two bulbs producing 72watts of light made it quite noticeable.The unit noticeably made a difference in indoor air quality in a very short period of time. There was a slight initial odor. However it was not unpleasant, but it was noticeable. This likely was from the bulbs doing a much better job of bathing the air conditioning coil in UV light. This killed off any mold and mildew that had built up after the previous unit had ceased functioning. After a short period of time of just a few days this odor faded away entirely as did other odors in the house which had returned due to failure of the old unit. We have the circulation fan and UV light running constantly to filter air and to equalize temperature out inside the house. I recommend doing this for maximum effectiveness in cleaning the air inside your home or business.