OK first thing, the 3d is a bit of a gimmick - but that is universally true, no?
I bought this on impulse having always loved Repton on the BBC (never played the c64 boulderdash).
I've found it very enjoyable, very quickly finding myself on level 50 of 100 in arcade mode.
For repton fans it slightly differs in that you can try an outrun falling rocks. This changes the dynamics of some of the puzzles.
Most levels can be finished on the first attempt (unlike repton) and you don't need to collect all the diamonds, just a target number.
There is also a puzzle mode that is more repton puzzle like, though with apparently small maps (8x8) in the early levels.
In all if you enjoy rock & diamond games it's worth the £15 rrp.