3mm LEDs are troublesome as they all come in different heights - at least all the hundreds I have bought were all different heights depending where I purchased them. The round LEDs - if they are too tall foul with some profile keycaps, so whenever I use 3mm round (which I don't anymore) I use a dremmel to take the top down. Now I just use 2x3x4 LEDs. The other good thing about 2x3x4, is, you can pull it right down into the switch, and it wedges in the small circle depression that is on the top of the switch for an unjacketed normal 3mm led, this means you can turn the board upside down and the unsoldered LED won't drop out. For both those reasons I find working with 2x3x4mm LEDs far easier and better, and I prefer the look at the end anyway.
