Keynote is hands down 100% better than PowerPoint. I've developed corporate decks on both platforms and the Keynote presentations are much, much smoother and better looking across the board -- and far easier to work with when you're building them. Like the other iWork apps, Keynote took a big hit after the golden era of iWork '09, when they iOS-ified and dumbed down everything. But it's come back pretty well. Recent versions of PowerPoint for Mac have gotten better, but they still don't touch Keynote.
Pages is a whole lot more streamlined and smooth to use on a Mac than Word. The basic stuff you need is there: style sheets, ability to work with graphics, commenting and revisions. Page layout features are quite decent as well, for basic stuff. It's no InDesign, but it'll definitely do. I'm sure there are esoteric things Word does that Pages doesn't. Again, while Pages will import and export .docx files, cross-platform collaboration is probably gonna be tough if you have to do it.
Numbers does basic stuff quite nicely from what I can tell. I'm not really an expert, but I've built some nicely functional spreadsheets to track money and other things, and if you're used to the other iWork apps, it will seem familiar. I know there are some huge power-user features that Excel has that Numbers doesn't. But if you're a spreadsheet pro, you're probably not budging from Excel anyway.