Michelangeli is the guy who's technique I love the most. It is all encompassing; it is above the level of the greats. Calling it godly would be an understatement.
Yes, his technique is a marvel of efficiency and control. His fingers are like little racing slot cars, which track with utmost precision.
And he lifts his fingers too 
Well, sometimes (albeit on extremely rare ocasions

) he even misses a note or two

.
But seriously, not to lift fingers should not be a self goal. It is rather a good indicator that everything is calm and relaxed, and with good control when your fingers are ready to translate the music image in your head. If for some reason (whether in order to create some special music effect, or out of physical necessity) you need to lift the finger--by all means, do it. It should be like your second nature--you don't pay attention to it, the music itself dictates your body what to do.
For marik: yes, I think the preoccupation with the 4th finger is mainly to do with trills and your advice about relaxation is noted. You were enormously helpful to me some months ago with the trills in Beethoven Op. 101 final mvt. fugue. Thanks so much. It works like a charm! But one of the biggest problems was keeping my thumb from being tense during 3-4 trills where the thumb had to grab at melody notes below the trill. The only way I could keep that errant digit from being tense was to meter the trills and practice slowly, slowly, slowly, synchronizing thumb melody note with the same trilling note above it. Ultimately, tension went away, but it really does lurk there for me when I'm trilling on 3-4 and plunking out the tune with the thumb.
Would you meter similar trills with thumb-tunes in Chopin, as well? Or just concentrate on relaxation and lightness? Metering Romantic period trills seems stodgy, somehow, but perhaps I'm wrong here.
I am glad that was of help. I meter all the trills and try to know precisely how many notes I have to play--this way they come out much cleaner and with better control.
Usually, instead of 3-4 I use 3-5. Just come from the point that fingers teach each other. So start the trill with 2-3 (or whatever you feel comfortable). See and analyze all your physical senses and try to understand presisely what you do. Then go to 3-4 with exactly the same sensation.
Trill is always a combination of two things--finger work and rotation (I actually call it hand vibration). I like to treat those two tasks separately at first, and then combine together.
The main thing is to do it slowly (but not too slowly, you still need the feel of the flaw) and lightly, analyze every little detail, and concentrate on relaxation, rather than forcefully "building the fingers"

. The technique is all about finger tip sensitivity and control. Any force brutally kills those.
Best, M