Dislike:
Fandumb. The only reason I like Touhou is because of the STGs.
Love/Hate relationship:
The UFO mechanic. It's terribly gimmicky, but chasing UFOs makes things a lot more interesting and gives me a rush that only late-stage bosses and post-stage 2 Cave games give me. UFO has probably the most fun stage portions in all of Touhou games because of this. But I can't convince myself that it is good as a scoring mechanic--since I'm still bad at the game, I need to play for survival and as such my scores suck balls. But at the same time, that gives it an even higher learning curve (meaning a longer life for the game) which makes it even more appealing. Also whoever said that it's bad as a resource management strategy, it is the ultimate resource management strategy. At least in order to get a good score.
Honestly, about the discussion in the first posts (no I don't think Bananamatic was trolling) Cave games and Touhou games are completely different beasts. Cave games tend to have a lot more aimed bullets (randomized as Banana said) which forces you to play faster and basically makes it less about memorization and more about reflexes, though memorization still plays a big part in it. Touhou has a notably inferior number of aimed patterns--in fact, most of the patterns are either static (to some degree) or completely random, and sometimes I don't see too much thought put into, for example, mixing a whole bunch of aimed bullets coupled with one or two enemies firing a static pattern during the stage portions, which leads to the blandness some people complain about in Touhou's stage portions. This is not bad per se, but it leads itself to a whole different style of play.
Which leads me to my ultimate complaint about the series: How playing Touhou makes me bad at other shmups and viceversa :V