Modal interfaces are bad practice for software that will be used by people with minimal training, in a "pick up and go" fashion, but they are not necessarily counterproductive for skilled experienced users. Douglas Engelbart was a strong proponent of modal UI's and IIRC did extensive studies showing that although disadvantageous for "newbies", such interfaces could eventually yield higher productivity. I don't know how much of this was simply due to his having such a small and biased sample. It is also important to point out that his conceptualization involved using a 5-key chording keyboard in one hand and a 3-button mouse in the other for most routine operations, so the modes helped extend the number of operations that could be encoded. Anyway, as someone who uses emacs instead of vim, on a regular old keyboard, I really can't say personally.
EDIT: I suppose many people use a program like Blender with one hand on a mouse/trackball and the other on a 3d mouse, so the point about having different modes to get more versatility out of the same few buttons is still relevant. With that approach I use the radial menus plugin for Blender which makes changing modes pretty painless IMHO.
Blender is definitely not modal in the Raskin sense. It extensively uses "quasimodes", but so do Raskin's own designs. That or the different view layouts mentioned by another commenter may have caused the confusion.
Modes are essential to complex, specialized software like this. As an audio engineer with vast experience in different DAW applications, take away my modes and take away all semblance of my productivity. :)
It's not just a workspace layout, it does have those but they're separate from the modes. Different modes (object mode, edit mode, sculpt mode, texture paint mode, weight paint mode, etc.) all have different hotkeys and in many cases have functionality that aren't available at all in the other modes. There are some conventions shared across modes, like G/R/S hotkeys for move/rotate/scale, or X to delete things. But the majority of blender's operations are mode specific.
If you're in one of the painting modes, F is the hotkey to change brush size. But you can't add faces in the painting modes.
If you're in edit mode, F will create a face from the selected vertices or edges. The concept of a brush doesn't exist here.
If you're in object mode, F doesn't do anything.
For another, I is "Inset Face" in edit mode, but "Insert Keyframe Menu" in object mode. This one is a bit different, because the keyframe menu is actually available in any mode and it just doesn't have a hotkey unless you're in object mode. But like the other mesh editing tools, Inset Face only exists while you're in edit mode.
EDIT: I suppose many people use a program like Blender with one hand on a mouse/trackball and the other on a 3d mouse, so the point about having different modes to get more versatility out of the same few buttons is still relevant. With that approach I use the radial menus plugin for Blender which makes changing modes pretty painless IMHO.