Given that the majority of PPL accidents are down to pilot error rather than mechanical failure, unlike IO540 (whose opinion I value but with whom on this I disagree) I see very little problem with a PPL flying at night.
Like the IMCr, it is good additional training (never a bad idea), and can eliminate some bad habits people get into in the relaxation period after achieving the PPL.
Flying at night is something I personally really enjoy. The scenery is different (and pretty), the skies are less populated, other traffic is far easier to see, ATC are less hassled and more ready to have a joke and to tolerate those pilots who are slightly less slick in their R/T, it is easier to book a club (or shared) aircraft etc. etc. etc.
I would caution PPLs that they do need a certain amount of instrument flying capablility. Apart from anything else, they do need to be able to transfer to instruments and hold an attitude immediately after lift-off until a suitable outside reference is visible above the engine cowling, and need to be able to carry out an approach trusting the PAPIs or only the aspect ratio of the edge lighting.
And on a lighter note, the checklist in case of engine failure at night is:-
LANDING LIGHT....................ON
If you don't like what you see then:-
LANDING LIGHT....................OFF
End of checklist.
And in answer to madlandrover, I concur with the D*ckheads comment. Even if you can't see the terrain you're heading for, coming in under some sort of control at low vertical and horizontal speed can be easily survivable for the aircraft occupants, even if going into trees (c.f. Dundee golfcourse). A Vne crash is not, under any circumstances.