Clean (Pale lagers, Kolsch) - 39%
Sours (Lambic, Flanders Red) - 27%
High gravity (Anything 1.100+) - 12%
Yeast driven (Hefeweizen, Saison) - 5%
Hop bombs (American IPA/DIPA) - 4%
Non-Reihentsgabot (Fruit, spice, or herb laced) - 4%
Malt driven (Milds, Dunkle) - 2%
Other - 2%
I won't say that the results from this one surprise me, but for once I'm with the dissent. With my brewing it's been the malt driven beers have always given me more problems than either sours or clean/pale beers. Getting just the right balance of malty flavors in a session gravity beer (neither bland nor obnoxious) is something I have yet to consistently master. Most other styles have something to camouflage their flaws (alcohol, hops, yeast, sourness etc...) but styles like English mild and dunkel have a clean/fresh malt character and not much else.
The "clean" lagers/ales are a similar category, but for whatever reason I've had better luck with my batches of Kolsh/Helles etc... maybe because they are so bland I keep my recipes simpler. Up until a year a go I probably would have rated hop driven beers as one of my biggest challenges, but since starting to keg those sort of beers have improved substantially. Non-Reihentsgabot beers also deserve a mention since they require not only a solid base beer but also layered complexity of adding a unique ingredient (especially when the ingredient(s) stray away than the handful of common fruits/spices historically used in brewing).
Anyone have a particular style/flavor that has been their white whale, something you've tried repeatedly to brew without ever really being happy with the results?