There are only 2 real flaws with this episode. Firstly, there's the "Touchstone" itself, which is pretty silly, and not in a good Stargate kind of way. Secondly, there are the people who use and own the Touchstone, who are a bit silly with their straw costumes and spears and such.
Another flaw with the episode is toward the end, when the Touchstone is returned. The choice of music at a moment that should be joyous is instead a mysterious, menacing piece. Whoever supervised the musical choice for that scene mustn't have been paying attention.
But apart from these flaws, the episode is well written, in particular the plot concerning the rogue operation. It's a very interesting idea, and it makes sense that this sort of thing would happen. In fact, apart from the Touchstone, almost everything in this subplot is realistic and believable.
However, my absolute favourite thing about this episode is the reappearance of Maybourne. Once again he is a joy to watch whenever he's on screen, and that first scene with him and Teal'c is classic Stargate.
Once again the positive aspects outweigh the flaws, making this is an above average episode. I would recommend it to any soon-to-be SG1 fan for the fact it plants the roots of the whole rogue-NID story arc, and hopefully they'll forgive it for the whole Touchstone thing.