The Mac Mini option is the cheapest around too.
Actually you can get Power Macs even cheaper. They can be found for almost nothing. But mini is really nice because of its size
I found the apps to be basic and unpolished. Web browsing was hit or miss and flash was, er, not so flashy.
Of course there's lack of certain apps, but if you compare to other amigaish systems, you can't complain. There are some really great apps which can be even better than similar apps on mainstream systems too. Like ShowGirls, MorphOS version of mplayer etc. Latest OWB is also very compatible with current web, it's very rare to get any "miss" pages, unless they lean too much on more complex flash things. Luckily HTML5 is coming nicely and that is well supported.
Although there is some TrueCrypt integration no real user based security is in place. I don't think full disk encryption was available (though it might be now)
I haven't tried myself, but from Kryptos readme:
* Encrypts an entire partition or storage device such as USB flash drive or hard drive.
That key is for that old, used G4 Mac Mini. When it breaks you just lost your MorphOS.
It's been said many times, if your machine breaks and you can prove it, you get a new keyfile for the new machine. And AFAIK, you can get it for any supported platform. Try breaking your HW with some other operating systems with different kind of licensing scheme and you won't get new version of OS for other platform, if you can't find similar HW anymore of if you'd want to upgrade at the same time.
BTW. has anyone's Mac mini got broken yet?
I don't think it's that big probability to break your computers in the time you would be using it before updating to faster/newer system anyway. On average, how many of you switch computer because it gets broken or you just want to get new one?-) Heck, my 80's/90's classic Amigas still work, as well as Pegasos1 which is years older than my current Mac minis.