Boy oh boy, Â this is a tough subject.
Learning mode patterns is just another way of playing the fretboard without thinking. Â It's a perfectly fine mnemonic device.
On the other hand, rather than concentrating on mode patterns, or any patterns for that matter, you'd be better served by understanding the why of modes first.
For instance, if you can start thinking of D Dorian as a minor scale with 3b, 6b and 7b, you are better off than just knowing a pattern, because you can apply that knowledge anywhere.
DMaj  D, E, F#, G, A, B, C#
DDor  D, E, F ,  G, A, B, C
If you know how to create a scale using wwhwwwh from anywhere on the fretboard, you are better off than just learning the patterns.
The main benefit to learning the different patterns is they allow you not to think, just play. Â If you want to play something in the late 60's jazz style, play Dorian mode. Â But since the patterns allow you to play without thinking, you better do your thinking first. :)
There has got to be a happy medium here. Â If you know all the patterns, but not how to use them, what good is that. Â If you know all of the theory behind the modes and scales but you don't have a method to play them, what good is that?
I think this analogy says a lot:
After 15 years of playing I started guitar lessons last week. My teacher gave me a handout with about 50 different right hand fingerpicking patterns and he gave me an exercise to learn that consisted of about 30 different chords (i.e. A+, CMaj7(b5), and stuff like that). I thought "I don't want to learn this jazzy #$#@%." But I went home and worked on them for about 15-30 minutes a night. Now I know several new picking patterns and about 30 new chords. I know them cold. So now if I am drinking some Jim Beam and jamming some blues with the boys, I'll occasionally throw in an "unusual" chord. The moral of this story is that it take a little effort to learn new things, but once you do you will always have them. You will never know how useful something will be until you learn it and then try to apply it.
I recommend figuring out some Steely Dan... there are some interesting chords in there, especially in their newer stuff.
