As someone who used to do web design when there were around 5 different rendering engines, I found having multiple browsers to design for was often a good thing. You could easily build something that worked 90% of the time on the primary testing browser, and hit a wall trying to fix the remaining bugs, but then testing in a different browser would reveal something obviously broken with your solution, and once you fixed that, would fix some of the minor quirks you were having a hard time solving in the primary testing browser. 5 was probably too many engines, and I'm thrilled to see Trident (IE) in the grave where it always belonged. But if you aren't testing in multiple browsers, you're making your life harder, not easier.