I'm not really much of an office suite user, but my experience and the feedback I've heard has always been yes it is bad compared to MS Office. I think Libre/Open office covers 90% of use cases and is more than capable of handling what most users need, however it's interface isn't nearly as good, it lacks the vbscript macros the rest of the world uses, it's charting/graphs don't look as nice and formatting comes out mangled when excel users open it (or when you open an xlsx). Microsoft has invested a lot of time, money and energy into getting Excel just right and it really is a great (if not their best) product. The heavy excel users I know that don't run Windows keep a Win7 VM around for Office/Excel use.
As a side note I think one thing that the Linux/FLOSS community is very bad at is learning from what others get right. You might not like Microsoft but to claim their popularity was in no way due to making some good products is disingenuous at best. If people genuinely care about increasing Linux desktop usage (which is not of any particular interest to me personally) the right questions to ask are about what MS and Apple get right rather than what they get wrong.