I have now installed several (2476D) Insteon SwitchLinc V2 Dimmers (among other devices as well) and had time to tinker with them a bit.  They are replacing standard relay switches, so having dimmers is a nice touch.

The switch paddles have the tactile feel of mouse buttons.  In fact they click like a mouse button does (although their range of motion is greater).  This is different from my old switches, but fine.  The led bar along the side is a great cosmetic touch, but adds nothing to the functionality.  The led's come as a standard white light which is arguably bright at night.  I like this in my hallway but not in my bedroom.  Luckily the leds are replaceable with colored leds which I found very nice, and reduce the amount of light.  The blue leds in the bedroom did the trick.

Their response to the local load is virtually unnoticeable, but not instantaneous like the old relay switches.  In most cases I have adjusted the ramp rate so it is completely unnoticeable.

Perhaps I have lower than normal ambient noise in my home or perhaps my ears are just sensitive, but I found that the switches make a very faint familiar electrical buzzing noise when they are on or dimmed.  The incandescent lights buzz a bit as well, however I have found that different brands of lights are worse than others.  This really isn't much of a problem, but I can hear it at night in the quite bedroom.  The switch buzzing is more faint when the lights are fully on, more noticeable when almost off, and there is no buzzing when off. 

When controlling linked switches, it takes less than a second to turn all of the lights on in the house.  There is a definite delay however it is short enough that it doesn't bother me any.

Smarthome also offers a reduced price version of the Insteon devices called the ICON series.  They do not have interchangeable led colors and do not have adjustable ramp rates, but if they did I would use them as they are half the price.  I should also note that the ICON series have a reduces wattage capability (which in most cases shouldn’t be a problem).

I have always been a bit rough on light switches and because the Insteon switches have such a mouse button feel to them, I find myself being much more careful with them.  This is unjustified as I do not know how much punishment an Insteon switch can really take.  Perhaps I am too gentle with the Insteon switches because I am not used to them yet, but in rare cases when I barely press the paddle I can hear the switch click under the paddle, but nothing happens (even on the local load).  I found that when I am in a hurry, walk into a dark room and quickly tap the switch (without fully depressing it) the light doesn't come on. I do hear the switch click (like a mouse click).  Other's have confirmed this as well.  It is quite infrequent though.

I also tested the X10 backward compatibly with an X10 RF remote control and an X10 RF receiver and had no problems.  Setting up the X10 address on the device was simple and ... it just worked.

The link/scene reliability has been 100% over the entire house!!!  Every light in a scene flawlessly turns on/off and dims/brightens properly.  All in all, I can not imagine spending the extra money on ZWave, UPB, Radio RA, etc where reliability is concerned.  Insteon is the most cost effective home automation lighting solution for its reliability.

However new devices have been slow to come to the market and the competition definitely has this to its advantage.  There are several software packages with beta Insteon functionality but they are still in their infancy.  Smarthome has plans to release quite a few new device types this year, including RF remotes.  Motion sensors and full software support have been requested by many people and based on the rumor mill I expect these to be available later this year as well.  In the time being, since the Insteon devices are backwards compatible with X10, one does have the option of using X10 devices in the interim.

If Smarthome and third party venders can produce enough new devices this year I believe the other automated lighting brands will have some tough competition.