There aren't "some problems with Office." It flat-out is broken. If you require MS Office for daily work, do NOT upgrade to El Capitan yet. Otherwise, it's a great upgrade, and definitely worth upgrading from Yosemite—but it's not an Earth-shattering upgrade. Wait if you wish.
It runs superbly on my 15" rMBP (except for Adobe InDesign, which pretty much runs like **** on any machine, under any OS version).