If by "all the notes the same length" you mean that:

   You can select the length you want for a note before you hit the key.

    All notes you put in will have that duration until you select a different note duration.

   You can select a different note duration when needed, for a single note or to continue with a new sequence.

Then you've got a common, and preferred, method for input for notation programs.

(By preferred method, I really mean that's the method I have preferred to use with several notation programs.)

A few exisiting programs make you click an icon to select the note duration. This is okay, but it's a lot faster if you can use a PC keyboard key 1=whole, 2=half, 3=quarter, etc to select the duration while you're in "step input mode." That way you can use one hand on the midi keyboard and the other on the PC keyboard, without tangling with the mouse.

Existing programs: Most use 1 for whole note, but a few use 0. Each step up divides by 2. Most of the "notation based" programs I've seen use higher numbered keys for shorter notes. I've seen a few "midi based" programs that seem to reverse the order, with lower numbers for shorter notes. This makes sense if you "think midi" (duration) but not if you "think in notation." Take your pick.

A problem with a "simple" note duration is that it will be almost impossible to notate "musical sounding" stuff without a way to deal with "tuplets." They occur far too often to be ignored. You can usually at least "fake" about anything with triplets, but fourplets and fiveplets can be handy on rare occasions. I don't think most people will use more than triplet construction for the majority of stuff, so I wouldn't worry too much about generic n-tuples, but you might want to leave a "hook" open to generalize later, if you can see a way to do it.

I'd say it sounds like a worthwhile addition to your program.

John