I've been very happy with gmail and have several shared calendars too. They do ActiveSync now for contacts/calendars, and hopefully email soon.
Not gone over to apps just yet, I have my own domain that forwards in to gmail, but when my hosting expires I might just do that. Only downside is the cool new stuff that Google does tends to take a bit longer to reach Apps users.
For the document storage, I can highly recommend Dropbox. They give you 2Gb of space, you run a client on your windows or mac machine and it syncs anything that changes, accessible from the web and iphone too. I use it to keep all my current and recent work on there so it's to hand anywhere I am. If the service ever went tits up, at least you've still got all your data locally!
Use this link: https://www.getdropbox.com/referrals/NTU0NDgzMDk and we both get an extra 250Mb over the standard 2Gb.