Hi vaporhat,
Congrats on your decision to "tackle" a lighting automation project. I imagine that when you write "the most robust" you mean the "most" features/capabilities. I'm pretty sure I can provide a more helpful response if you can indicate the feature-set that best describes the options and considerations that are the most important to you:
Your "feature-set" of what you consider a robust system might include answers to the following:
What is your approximate "budget"?
How-much over-budget are you willing to go to get everything on your list?
How much "programming" do you want to do?
How much "skinning" do you want to do?
How many lights/loads do you want to control?
Will you be using timed events?
Will you want to use external triggers?
How much control (outside of xlobby) do you require?
Do you need the system to provide interfaces other than "lightswitches" - such as keypads or remotes?
What companies' hardware looks good to you? (maybe multiple)
What companies' hardware feels good to you? (maybe multiple)
Is the look/feel compatible with everyone who will be using the system?
(A "custom screwless keypad with "cool-looking little buttons" vs. "a light-switch that is easy to hit in the dark")
Does list of old problems that the system solves outweigh the list of new problems the system will create?
All of these considerations may ultimately play some role in your decision process, and in the end, you may find that you have to compromise a bit to get the best system for your budget, application, and WAF.
Absent answers to the afore-listed "questions", following is my general experience with lighting control and XLobby:
My experience with the follwing is listed for what little help it may provide (you probably already know most of this stuff, but here's my mini-evaluation anyway):
X-10:
Relatively inexpenseive.
Available almost everywhere.
1-Way only - "Did it turn-on?".
Easy to set-up the X-10 hardware.
The protocol can to be somewhat unreliable depending on many factors.
Insteon/Pulsworks/UPB:
Also relatively inexpenseive.
Good replacement/upgrade for old X-10 hardware.
2-way connectivity - "Yes, it's On/Off"
Reported higher reliability than x-10.
I have not confirmed "higher reliability", but I have,in-fact, ordered the UPB components to replace an existing (small <8 devices) X-10 system that is experiencing some reliability issues, and for which I'd like 2-way communication for "status", and I have ordered the components to add some XLobby UPB control to some "lamps" and other "triggers" in my home.
Centralite:
Centralite is a U.S. based manufacturer of lighting control products that I have used in the past with good results. Their programming interface along with some other resources are available for download from their website, and their engeniers will even take phone calls from consumers. They provide both IR and RS-232 interfaces, but I have not-yet integrated a Centralite System with XLobby. Centralite is also an excellent value. As soon as XLobby's RS-232 interface is ready, I will be integrating a 190+ load Centralite Elegance system with an XLobby server in a 14,000 sqft house. If you email me, I'll let you know how it goes.
Lutron Homeworks Interactive:
If a "stand-alone" lighting control system from the likes of Lutron or others are more of what you had in mind, I can tell you from experience that the Lutron Homeworks Interactive system has "tons" of capability, is VERY stable and integrates beautifully with XLobby(V3), but:
It is expensive and,
...you'll have to hire a "Certified" Lutron HWI Installer and...
...they typically charge about $125.00/hr.(In Southern CA) and...
...they will require you to pay for about 30-40 hours of "programming" to do the "initial programming" for a 40-60 zone system, and...
...you will NOT get a copy of the software they use to make any adjustments to the system programming so get ready for a $125.00 - $250.00 service charge any time you want your "certified" installer to change something as small as the programmed dimmer preset level on a particular lightswitch.
On a brighter note, Xlobby's new Lutron Service can make the Lutron Processor do pretty-much whatever you want.
Other manufacturers you may want to check-out are "Lite Touch" and "Vantage" they both have some "cool-looking" keypads, have been around for a while, and offer RS-232 support. (But as with Lutron, you'll likely have to hire a "Certified" installer to use one of these "High-End" companies.)
In short, the look and color of the wall-switches you want or don't, your budget, and whether you want a "stand-alone" system that will work with or without XLobby can influence your "optimal" system. If you take a look at the websites for the brands mentioned, you'll likely get pointed in the right direction - at least in terms of what questions are most relevant to your project. Then you can ask "us" how our experiences match a particular manufacturers' claims.
I sure hope that helps.
Samson