I've used theknot.com for my wedding site, for some checklists and a few other things - starting as far back as 12 months before the wedding. I'm really glad I didn't do more using it, because they decided to do a no-notice 100% site overhaul of ALL features. The new site is buggy, has features that are less rich, and while snazzy just doesn't do what you need.
For example - their upgraded checklist suggests I don't need to worry about caterer (I'm 60 days out... caterer's been booked for 4 months) because "you checked a lot of boxes today, you worked hard, take a break".
Our site was down the day after we sent out invites because they didn't think about websites that use a redirect (www.myNameHerName.com ==> knot.com/*******/). Awesome. Now nobody thinks our site is up.
I'd be super pissed if I'd been using it for budgeting or more items than just our site and a rough use of the checklist.