I got something I thought was a shite spawn for quite a while. Spawned on a fair-sized island made up of NOTHING but giant fir winter forest biome, with the FTB Beta A pack. I tried to stick it out, and noticed that the Extra Biomes woods couldn't be used for some mod-related craftings. However, after digging down for what was -going- to be a bedrock mine, I happened across some stone brick. I broke thru that, and lo and behold, I'd hit a stronghold! Under 150 meters from my spawn. Needless to say, I moved in and lived as well as could be.
My worst ones tend to see me spawning in a treeless meadows biome the size of Texas, bordered by ocean, and some kind of winter biome. What's worse, a hell spawn point I had in one of my worlds placed me right on the EDGE of a tiny island of netherrack floating at about Y-level 120, with nothing but lava to break my fall, should I go down. Another irritating biome to spawn in is the weird swamp-type biome that Extra Biomes brings in, with small lines of dirt and deep-ass water holes between em.
Oh, and one time, I spawned on an island that spawned nothing. But. Pigs. I NEVER saw a single cow, sheep, or chicken. All pork, all the time.