I plan on buying the RUC, I looked at the specs on the ISY99i but haven't found any docs to read the particulars.
Both sound very similar.
Both have the ability to configure their networks over the web and to issue timed and triggered commands.
The ISY states it has 300 programs, the RUC does 99 (TIM timer limit). I don't know if the other RUC trigger based links - daisychained links - are part of this limit or not. The RUC can have 20 delay timers running simultaneously.
The RUC is stated as having the functionality of the TIM-01 timer built in. Read the specs on it, the timer alone is ~$100.
The TIM is a pretty robust timer with links based on 3 categories, 4 execution schemes and has a random time generator built in for vacation lighting. I run the USC timer (SA version of the TIM) now with my OmniPro install to take the vacation program burden off the main controller.
However, I don't see the area in the docs for programming the timed events. I'm wondering if this is in a planned firmware revision.
You do set the time, lat/long etc. Thise things are for determining sunset/sunrise, which implies timed events are possible as stated in the spec sheet.
From the review here on Cocoontech (looks like the docs haven't caught up):
"UPDATE #2: Web Mountain has released a firmware update which adds support for scheduled tasks, based on time of the day, sunrise/sunset, day of the week, home/vacation mode and they also support a 'random' feature, which creates an offset between 0 and 30 minutes. This will allow you to create a schedule which makes it look someone is actually at home. "
Those are eactly the TIM commands.
The ability to daisy chain UPB commands is very powerful. Trigger a UPB command upon receipt of a link, with a settable delay if desired. Again, in conjunction with a dedicated controller, this can take some of the burden and leave the controller program lines for more involved automation. Or it can be used as a base line controller all on its own.
The ability to send e-mail based on received UPB is nice. Combined with an IO module to add relay control and dry contact or other inputs this can take be used as a base line controller in an all UPB install for some very powerful things, garage door notification, driveway or camera motion, etc.
The RUC has a second serial port and the processor has a wireless channel, both not yet enabled. The second serial port could tie in something like an Ocelot into a networked system. At a very low price point.
Ihe IP LAN port and ability to send individual UPB commands opens up the door for interface with very robust remote apps and IP based Apps on something like an I-phone or I-pad. This appears to be two-way if implemented properly.
The ISY specs don't mention e-mail or a second port.
I assume "triggered" events on the ISY are the same as the daisy chain links with the RUC, the ISY specs don't mention whether these can be delayed or not.
The specs don't sound much more robust than the RUC, but again I have not been able to read the docs themselves.
Bottom line they both sound very similar. Price advantage goes to the RUC.
ETA:
Looking at Lou's post below, looks like the ISY is much more of a controller than a programmable interface.
Probably why the price difference is so great.
Reading the docs, the RUC has an IR and wireless version coming plus an "advanced" version which may ultimately have similar functionality to the ISY.