As with any piece of software, peoples' experiences will differ. I find iWeb quite intuitive and easy and have thrown together numerous sites with ease and have not run into the trouble(s) that others have reported... my Quicktime movies play flawlessly across browsers/platforms, my images all look great, and the navigation works a charm... then again, I can't say whether my usage differs from others' and what exactly they're running into trouble with.
At any rate, like we both agree I believe, iWeb should be relegated for use by those with little to no experience with the "code" behind web pages, and for those who just want to throw together a very nice-looking web page or pages with drag-and-drop simplicity and iLife integration. For anything beyond that (JavaScript, php, database integration, manual code modification, tight control over placement of elements, etc.), I recommend finding a different "rapid" web page development environment... you mentioned a few, and I've also heard good things about RapidWeaver.