What do you think of letter thickness and proportions in this word?

If the word is part of a larger logo, then nitpicking it as a stand-alone element is fruitless. It would have to be seen in context. If it's the entire logo, than it appears somewhat elephantine - more so in the reversed version. If it's to appear both black on white and white on black, the word should be optically corrected to look the same in both environments. And it will be different when printed than on a screen, and different depending on the sizes and resolutions of the media.
The space between the L and O will disappear in some sizes and circumstances.
You asked if it's OK for the L and E to have different dimensions - if it looks right, then yes.
To me, the spaces between the E's crossbars look very small. The optical effect is that the E's top and bottom crossbars look considerably fatter than the L's horizontal, even though they're the same. That may be why eliason said to make L's horizontal wider.
You're trying to design a VISUAL identity, not a mathematical one. What you SEE is always more important than what's actually there
- Herb
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