I switched from Dropbox to SpiderOak recently, and they're a bit better, but feels so clunky. I'm just about fed up with all of them. I use CrashPlan for backups and they're at least good for CPU usage because they have a preference -- max CPU (%) when you're at the computer, and max CPU when you're away, which really does help.
Those who are using Dropbox may find something like cpulimit[1] useful. This limits the CPU usage of any process by repeatedly sending SIGSTOP and SIGCONT signals to your process. It's on homebrew for OS X. I think there're some other alternatives available too but can't remember off hand. But if the article's accurate, Dropbox has issues even when it's not indexing heavily.