Far easier for the vast majority of users already. Download, move to Applications, done. Automatic updating via Sparkle. It ain't exactly rocket surgery.
As far as typical unixy tools, homebrew (http://github.com/mxcl/homebrew) does a pretty fantastic job.
Not exactly 'move to applications'. And if some package is only available in source you're really in for a rough ride.
It's been a while though (about 2 years), possibly it's much easier now than it was then.
I use my mac so little now I've borrowed it to a friend here that does design. Too bad in a way because I really like the machine, it's so quiet compared to the pcs I use.
As far as installing things from source that also has improved greatly in the last two years as well, so there's that.
But in general I'd say the user experience when installing applications on the mac is certainly miles ahead of the way Windows typically works, and arguably better then even Linux (Ubuntu or similar) with the gui frontend to apt-get.
Personally I expect to just see the prices of software to come down on Mac and Windows but start charging on Linux if more people start using it. A couple of bucks is no big deal if the software is easy to buy.
For every package on the windows platform there were suddenly 3 or more competitors available, 90% feature complete in a race to the bottom for marketshare, which they all got and then suddenly figured out they had to make money somehow.
And then they imploded, but the damage to the market was done, everybody expected 'free'.
Apple has bucked that trend to some extent, but I don't think this was a reversible process, all software, including operating systems and so on, with the exception of niche code and in-house software for deployment in a company, some firmware or as a back-end for a service will be free. And even some of the latter will be free (see 'reddit').
So, I changed tack, way ahead of the pack I aimed at a service driven income stream rather than selling bits of software.
My then partner Michael saw it coming with great clarity and together with another guy called Paul (who was founder of one of the first ISPs in NL) they changed my future in a fairly dramatic way.
So if you haven't seen the elephant yet, maybe you need a higher ladder, but he's coming for sure. None of the 'old' ways of making money can be taken for granted. Read 'being digital' by Nicholas Negroponte if this hasn't convinced you.
It's old (by internet standards) but it is in many ways a visionary book. Far more so than Gates' 'the road ahead'.
Then iTunes came along and showed that actually people just wanted (a) to not pay such a rediculous amount and (b) to be able to conveniently get the product. $15 for a CD that has just one song I want? Nah, I'll just download it. $1 for exactly the song I want and I don't have to mess around with torrents and shady software and sites? Done deal.
If it was as easy to apt-get some package on to the mac as it is to install stuff on most linuxes (or 'yum' if that's your flavour) I think that would change matters considerably.
The initial hurdle to deployment is the hard one, if there would be a package manager with a sizeable repository installed by default on OS/X I think it would make life much harder for those earning a living writing software.
Just like 'tucows' changed the world of closed source utilities for sale on the PC platform, only then a bit more dramatic because the vanguard would already be pre-installed.
Openness includes removing barriers to getting at stuff, not just that it is 'open' to modification, I suspect the majority of the 'hackers' on this forum have never modified a line of code in most of the stuff they download and install.