Bought this app a few weeks ago to access Dropbox as an online drive, has treated me very well. The offline sync feature has been super-useful.
ExpanDrive version 3 worked well for me and I purchased version 4 when it was released. I also purchased the Lifetime update. It quit working almost immediately. Jeff responded once with basic support. I sent him requested info and I have never heard from him since. I have emailed two more times, but it's just a black hole for me now. Recently I bought CloudMounter from the Mac App Store and it works perfectly! Also unlike ExpanDrive, CloudMounter has a well thought out interface. Other than the money I lost with ExpanDrive, CloudMounter has mad me completely happy! Check it out.