That's good to hear - ideally, I'd like pen/character input to be looked up automatically, and keyboard/pinyin input to require hitting enter before searching, but I guess that's getting way too specific.
By the way, for anyone who is considering getting a Clie UX50 (or some other Clie variant) to make use of the keyboard for pinyin input: it's actually a lot faster, for me at least, to use the virtual keyboard or graffiti on a Tungsten or something similar. It's kind of hard to type with one hand (which you might be doing while reading) and even with two hands it's not a whole lot faster than virtual keyboard, since the keys are so small you need to thumb-type.
Also, since it has a hinge screen, the screen will get pushed back while you try to write on it until it locks at the fully open position. It's less than 180 degrees when fully open, so if you have it on a desk the thing will rock back and forth while you try to write on it. You really need two hands to use it, or use it in Tablet mode (which defeats the entire purpose of having a keyboard).
The processor is somewhat slower than a Palm Tungsten E, so there'll be more of a delay with searching after HWR input, and you'll need to turn delay/search button on to type quickly on the keyboard (it'll keep trying to look things up after each letter and not process the keys you hit). Delay/search is kind of annoying, because character input gets slowed down (either you wait for the delay to run out or hit the search button every time) and if you're too slow when you're typing and let the delay run out, it seems to reset for a while (e.g. looking up every character you type in, instead of delaying).
Personally I think the optimal way to use it is just with virtual keyboard, since you type while in the keyboard screen (and avoid Pleco trying to search after every letter). The Clie has the added nuisance of requiring several steps to access the virtual keyboard.
I would definitely suggest processor speed as one of the main things to consider when buying a PDA for PlecoDict use.