Price-wise, for occasional use the Econotig is a great little machine. If I recall correctly there is no option for water cooling, which means if you have a lot of work to do, you're going to be spending a lot of time waiting for it to cool down. If you want to make tanks, while welding the end caps on you probably won't make it all the way around before overheating - every time you stop/start you increase the chances of pinhole leaks.
That would be the situation for me even with a more full-featured machine. While I am competent with a MIG machine, I haven't mastered the wire-feed technique for TIG. Most of the aluminum stuff I've done is serviceable, but not too pretty.
At $800 for lightly use machine, I wouldn't think twice. Snatch it up. When you outgrow it, sell it and trade up.
A word of caution - once you start down the dark path, forever will it dominate your destiny.
- tubing bender
- plasma cutter
- once you've mastered aluminum, you're going to want to remake all the stuff you made in aluminum only this time in STAINLESS!