Miller;
I have both a Mk6 Carbine (16 inch barrel, folding stock, etc) and a Mk7 (4 inch barrel handgun version).
I honestly don't fire the Mk7 much, as it's rather unwieldy, but I couldn't pass it up when one came available some time back. Accuracy wasn't bad, but it's not exactly the handiest thing in the world.
The Mk6 is a pleasure to shoot. Accuracy is solid, and while I haven't fired for pure accuracy at 100 meters, it will easily do a soda can repeatedly at that range. I've also not had any reliability issues with any of the ammo types I've tossed through her.
34 round Sterling mags run about $40-50 in the places I've seen them. You can also use Sten and Lanchester mags, but the Sterlings are well worth it in terms of reliability and ease of loading.
I haven't handled any of the conversions, though I'll have to look that article up. If they're the same folks who were doing the conversions from Stens a few years ago I seem to recall that they got rave reviews. It would be quite nice to be able to get another couple
Prices for original Sterling-made Mk6's normally seem to run right around 1000+ from what I've seen. For what it's worth, I know the American Rifleman did a review of them back in 1988 or thereabouts when they sold for about $650 new IIRC.
If it's the side magazine thing which interests you, you might also take a look at Catco's SA2 sten carbine, if they still have any. They're roughly on par with what you'd expect from a Sten, but they're a fair sight cheaper than the average Sterling. DMAX Carbines, which are in 45 ACP, can also be found from time to time. Most of those I've seen run about 500-750 or so asking price.
Hope any of this rambling helps.