Lots of the SDK feels poorly-thought-out, even relatively recent additions.
Some things that exist for both Web and Android are worse on Android, inexplicably (Location for instance).
Lots of Googling a problem, finding a bug report for it from 5 years ago, and reading in the comments saga of "not a bug, intended behavior", "no, seriously, it's a bug, learn to read (x10)", then a stretch of months of "will you please fix this? It's a big problem.", "here's a workaround", "thanks!", "here's the fix, it's a trivial 2-line change, please pay attention Google!" then a silent "CLOSED DUE TO BUG BEING OBSOLETE", then several, "but wait, this still happens in the latest. Do you guys even test?", the last of which dates to a week ago.
[EDIT] Oh, and mediocre technically-complete-is-the-best-kind-of-complete documentation full of bad examples (to the point of being outdated and broken, sometimes) and bad advice.