I think you should ignore people who don't like 4-way movement and go on. 4-way and hex-based movement have both some advantages and some disadvantages over 8-way movement. Even if 8-way movement has more advantages, it is better to add more variety to the roguelike genre -- you will probably lose people like Fenrir, Kalantir, and Krice, and possibly those for whom your game would be the first roguelike (as I suppose 4-way movement would be strange for them... but I am not sure), but get those who like this idea or just like variety. It will be harder to create the "best roguelike in Universe", but easier to create an original one. (Unless your plan *is* to create the best roguelike in Universe, of course.)