My main gripe with openwebui, in addition to it being slow is the fact that it mangles documents in the OCR step. tables that could have been understood great by an multi modal llm, just gets mangled by the ocr and lost instead of storing both a text and original representation.
Being able to properly searcbin the knowlege base lime the llm does, but manually would be nice (like get recommendations for docs to add).
My usecase is mostly writing, so having a integrated document refinery editor is also a nice feature list.
I'm probably rambling but these are my base use-cases for a llm ui I personally have found.