I use SmartThings as the OpenHAB time/value tradeoff didn't feel like it made sense in my use case. This is worsened by the lack of a usable open Z-Wave security class preventing locks from working with OpenHAB.
I feel like OpenHAB has a lot of potential, but it suffers from the sort of things that a lot of open source projects experience: poor (or completely missing) documentation, dated user interface, coupled to an aging architecture in need of a re-write. I intend to give it another shot once 2.0 stabilizes a bit, but without lock support it cannot become the centerpoint of my system.
Also check out HomeGenie if you're looking at open source alternatives.
So I'm not so much answering your question about whether or not to migrate, but I do want to tell you about HomeGenie. If you have a machine you can use as a server (I'm using a Raspberry Pi), it's something you should check into. You mentioned having a desktop controller, is that the CM15a (ActiveHome Pro)? If so, HomeGenie works right out of the box with it.
To me, Home Genie is somewhere between a full-blown automation system like OpenHAB and just simple remote control. What I like about it, is that I was able to control and program my X10 devices pretty easily, as well as have a nice remote interface for them. It works with a lot of other technologies too (my IP cams are also set up with HomeGenie), so if you do decide to migrate, you can keep using your X10 devices alongside the newer stuff (like Z-Wave and Hue).
Cool, thanks for the detailed reply. I'd really like to pick up some Hues, but the price point has been the main barrier for me. I just heard about some cheap Chinese lights called MiLights or something that are very similar but much more affordable.
> I reckon OpenHAB might help with the GUI in a big way? (I'm good at making little hacks/scripts but royally s*ck at GUIs).
Honestly I don't know, as OpenHAB is a bit beyond me (I installed it once, but I'm really not a programmer, so I was lost). I believe there's a component called OpenHAB Designer that lets you design the GUIs.
Other setups you might want to look into are OpenRemote (more of a remote program than actual home automation) and HomeGenie. I'm using a VeraLite now, but I was using HomeGenie for a while. After playing with OpenHAB and Open Remote, I felt like HomeGenie was kind of in-between those 2, in that it wasn't as complicated as OpenHAB, but had more automation features than OpenRemote.
Anyway, if you have any other questions, I'd be glad to answer them if I can. And if you haven't already, make sure you come check out /r/homeautomation, there's a nice, helpful community there that can answer any of your other questions.
What sort of lights are you planning on using?
If it's just a few lights, I'd personally just write up a few python/php scripts to turn them on and off, and check their status. I found something quite like what you wanted, but it seems like overkill. http://www.homegenie.it/docs/index.php