These problems are something that modern post techniques can mitigate. Until relatively recently, most Super-8 transfers were primitive, often relying on not much more than a video camera aimed at a projected image. Because Super-8 was invariably shot at 18 frames per second, this can cause problems with flicker, double images, and issues with focus, steadiness and colour which can affect any projected image. Better techniques involve a proper per-frame scan of the film, with the frame rate conversion made later, in software. Modern telecines can often do this, although the last time I checked, it was difficult to find any facility which owned a Spirit and had actually bought the 8mm gate accessory.
Superb work is being done with both modern and historic 8mm material by interested individuals with custom built gear, particularly Belgian Super-8 enthusiast Freddy Van de Putte, whose work with modified projectors and machine-vision cameras, along with careful digital processing of the captured frames, has produced superlative results. It's a bit of a stretch to contend that Super-8 really requires HD resolution to capture all of the information, and the 1388x1036 image seems more than adequate. Particularly interesting is the use of software stabilisation, removing the jitter that's part of all Super-8 and massively improving the appearance of the footage. Colour correction and noise reduction can both help too, although I do know some people who'd probably complain that it no longer looks like Super-8; it looks like bad 16mm, which is a pretty significant achievement!
Super-8 itself is a development of an earlier format which had somewhat larger sprocket holes, resulting in a smaller image area. Enthusiast variations on this approach, including using the area between sprockets for a wider image or using the now-redundant soundtrack area, are generally aimed at shooting a bigger image for better grain and resolution performance and rely on modern scanning techniques to accommodate the new frame sizes. Whether these sorts of experiments really constitute a future for Super-8 is hard to say, but with Kodak seemingly aware that their own future lies in people with a specific enthusiasm for film they've released new stocks as recently as late 2012 and the future is not as dim as one might have expected.
Some examples of Freddy's images grace this article, but you can find more information on his site at www.super-8.be, and view some surprisingly sharp 50D-originated material below: