Gino:
Actually, the reliability problem with the hi-cap Maks was with the cheap aftermarket mags that were sometimes sold with the pistols. Using the now easy-to-find factory Russian mags cures the problem virtually every time.
As for the adjustable sights, a few people have reported problems, but the problem does not appear to be widespread. The usual fix is to use a dab of temporary threadlock to hold the sight in place.
Reprobate:
If you lurk on the Mak Forum for bit, I think you'll find that 9x18 is the caliber of choice, although there's not a big deal made about it. 9x18M in its hottest form exceeds most .380 ammo by a slight margin, but not so much so that it makes .380 obsolete by any means. There are some fine .380 factory loads available. Also, as you mention, .380 is readily found most anywhere -- although 9x18M is pretty commonly available now too. Unless there's a real burning desire to shoot 9x18M, there's no big reason to dump the .380 barrel. On the other hand, for under $75 shipped, you can get the barrel and barrel pusher from Makarov.com.
And about the price of Russian commercial Maks to Bulgarian Maks, the main reason for the higher Rusky prices is that they are no longer imported (also, some claim that the Russians digest JHPs slightly better than other Maks). Recently, there was a glut of Bulgarians that flooded the market, helping to keep the cost of them down. But there are signs that that supply is now dwindling. From a reliability and accuracy standpoint, they'll hang with the Russians all day long. They also tend to have better bluing and less sharp edges than the Russian commercial Maks
But in any event, regardless of caliber or country of manufacture, there is not a Makarov I wouldn't recommend. My advice is to buy the one that floats your boat, or buy the one with the best price.
Take care. Marko