xbomb rules! Does anyone keep a public record of high scores, especially for triangular grids? Triangles require more skill and involve less luck. Square grids often require the user to take a chance in order to proceed. Minimizing the chance you take may require skill, but if you are faced with a simple "acey deucey" 50% chance choice, as frequently happens on a square grid, this is just boring. Such situations occur much less frequently with triangles.
Heh, xbomb 2.2 with improved mouse options and different color numbers was released back in 2008, but in August 2010 the latest stable Debian "Lenny" still has 2.1a. Maybe the upcoming "Squeeze" release (which was just frozen) will have 2.2 for those of us too lazy to download it separately.