Imo UFO does have a weird difficulty jump, in that...
If you can barely dodge the stuff, in other games, you might clear 0/0 or something,
but in UFO you will die horribly.
On the other hand, if you are very comfortable dodging the stuff,
then UFO would not be very hard as you can collect bajillions of lives/bombs.
For me, UFO does cause more rage than any other game (except DS/StB, but I don't really play those)
Oh, and maybe I suck too much, but somehow I can't get used to SakuyaB in PCB...