Dave,
How about on the hardware side? X-10 modules require you to open up the switch to change the codes. Insteon can be done by just tapping the rocker and I think UPB actually does it remotely via the computer. I am now (as a workaround) thinking about changing the codes on my modules to help speed up X-10 response. So just from the point of view of hardware, it seems to be more time consuming.
Ahhhh...now the software, haha. Well, there are a lot of little tricks to get AHP going...from hardware mods to software settings, to having to use very well thought out programming schemes. It is my understanding (and may be terribly flawed) that other setups don't bog you down with these issues (at least not to the degree of X-10).
Now, of course IF you know what you are doing...like you do Dave, its not such a big deal. And now that I am on my way to understanding a lot of this, I can make it work. BUT, my fear is that as I grow in complexity, things will start to become unstable and continue to require more and more effort to work. By noooo means am I anyone really to listen to about this! But consideration from other sources like cocoontech should be given.
What I keep seeing over and over again is that X-10 is great for the hobbyist...and it truly is. It is the most flexible, cost effective solution out there...but the very nature of a hobbyist is that you will have to tinker with it (and there is the rub). However, my understanding is that UPB is solid and just works (and Insteon is somewhere in between but getting better). The downside is that of course those costs a lot more...way more and do not really have X-10 equivalents (such as slim switches and motion sensors).
One may want to decide if they are a hobbyist or if they just want a solution. Personally, I am on the fence. While I like to have fun getting it to work, at times I am frustrated because I want to be 99% condifent in my solution. Anyway, I just want to portray (as fairly and best that I know) the different systems. Besides it does make sense that the more recent solutions out there have inherently better reliability...after all, X-10 is quite old considering the rate of change in electronics and technology.