In Mountain Lion, the new Messages app replaces iChat.
If you're the kind of person like me who religiously keeps your email, chat logs, etc, but you have chosen not to do a migration of your data when upgrading to Mountain Lion, you're going to be faced with the problem of how to import your old iChat logs into Messages.
My first desktop Mac was a IIcx, bought in about 1989, for the astounding sum of nearly £4000 (to put that in context, it took me a year of working between school and university to pay for it, and I could have bought a new Ford Fiesta for less).
Since then, as a Mac developer, I've owned and used many more, pretty much always the top spec of the current generation. There was certainly a time when having the latest, greatest desktop machine was essential (not to mention highly desirable for the sheer geeky joy of it).
However, since going back to indy development in 2010, I've only worked on my laptop, and I didn't have a desktop machine at home for a good few years prior to that, despite regularly working from home on a big game with masses of data.
So the recent speculation leading up to WWDC about whether the Mac Pro would get an update, and the subsequent answer ("not really, well maybe slightly, but there's something new coming next year"), lead me to ponder what I'd actually want.