Ah, Repton. I remember it driving my Dad and myself insane when we played it on our Electron some time in the 80s. Repton3 it was. I remember sketching some of the boulder arrangements on bits of paper so I could ponder the solution whilst away from the computer.
As an out and out puzzle game it rocks (no pun intended). The rules are simple and strict. TBH I think I've got more drawn to free-form, open games such as Grand Theft Auto or perhaps Quake where there is more choice as to how one tackles a problem. I'm not sure I could return to the confines of Repton (and I don't know if my brain could take it again =)
Regarding the graphics: I'm just taking it as a new way to continue playing an old game. As you said, an emulator is another way to do it. Either way I wouldn't expect better graphics. Now, if there was a new Repton, then I'd expect the bells and whistles.