If Trillian focused on solely developing its IRC support to compete at mIRC's level, it would be a VERY tempting alternative.
As it is, the lack of scripting and other such goodies contribute more to its reduced stake in the market than the state of its graphical interface ever will.
As for updates -- most modern development programmes run far faster than mIRC. You can *certainly* expect more than a couple of updates per year -- especially if the application has not changed considerably for several versions.
