I'm probably one of those "heavy users", though I've only been using it for a month to see how well it does. Here's my review:
Large completions (10-15 lines): It will generally spit out near-working code for any codemonkey-level framework-user frontend code, but for anything more it'll be at best amusing and a waste of time.
Small completions (complete current line): Usually nails it and saves me a few keystrokes.
The downside is that it competes for my attention/screen space against good old auto-completion, which costs me productivity every time it fucks up. Having to go back and fix identifiers in which it messed up the capitalization/had typos, where basic auto-complete wouldn't have failed is also annoying.
I'd pay about about $40 right now because at least it has some entertainment value, being technologically interesting.