The Extra in its original form, the full-scale aerobat with a human pilot, is one of the very best in its class. It's possibly the most kitted and ARFed aerobatic design in the RC industry. With all these many versions, the production quality and design modifications vary all over the lot.

One of the definitely good versions for breaking into RC aerobatics is the Sig Somethin' Extra, which I know comes in kit form, most likely it's also ARFed. The Somethin Extra is not a true scale model, since it has a thick airfoil, low aspect ratio wing, which makes it a lot more flyer friendly, less stall-prone. Much of the difficulty people have in moving up to the more scale-like models is with tip-stalling or unintended snap-rolls--because of the tapered wing for one thing, excessive control set-up for a second, higher wing-loading for a third--plus inexperience of course, since all these tendencies can be avoided, once you know how.

At the fields I fly the Somethin' Extra is very popular as first low-wing symmetric airfoil model, and some guys have fun flying them for years.