1. How significant was your weapon damage at mid- to high-levels (let's say 8th+)? A poster on the paizo forums made a convincing argument for the magus' melee damage being almost completely irrelevant to his overall damage potential, does that match up with your experience?
1d6 + 3 (enhancement) + 2 (weapon specialization) + 8 (dexterity) + 6 (power attack) + 1d6 of some elemental damage usually, for an average non-crit of 2d6+19.
The real damage comes from using a point from your arcane pool to throw that elemental damage on there, together with keen. It gave me a crit range of 15-20. The kensai archetype gets its intelligence modifier added to critical confirmation rolls - I think my intelligence was around +5 or +6 modifier at that level. I also had the critical focus feat.
How that works out is a 30% chance of threatening a critical, but an 80% of confirming any critical that hits. The kensai also has an ability called perfect strike - 2 arcane pool points when you crit to increase your critical hit multiplier.
I could burn through my arcane pool very quickly if I wasn't careful, but throwing down 3d6+57 felt pretty good.
Meanwhile, at 15th level I had a +11 BAB and was almost always hasted, so four attacks, plus if I use a touch spell I get a free attack to deliver that with my scimitar at my highest attack bonus. In other words, 5 attacks, 3 of which were at the maximum. We'd fight things that were immune to electricity (demons, e.g.) and I would still cast shocking grasp just to get that extra attack.
That's probably way more than you wanted to know.
2. ARcane Accuracy is my first chosen arcana. Are there any others that you found particularly useful? I'm find it hard to come up with many that I really like to fill all the available slots by mid- to high-levels.
Wand wielder was nice (low level shocking grasp or frigid touch spell to get the extra free attack each round). I always wished I had taken "close range" because it would let me use ray of frost to get that extra free attack. "Critical Strike" let me cast a touch spell as a swift action and deliver it with an extra attack once per day. Bane blade is nice.
Spell shield is bad, imo. You get your shield bonus from the shield spell and your intelligence is not likely to provide a much higher bonus.
3. I'm definitely going to be hunting for a Ring of Wizardry. Are there any other items that you found particularly useful for you?
One of your advantages over a more conventional fighting class is increased mobility. You can be "sticky" with flight and teleportation style spells to pursue casters. Items that help you there are great. Boots of springing and striding or ring of freedom are particularly good.
It was kind of a low magic game so I didn't get either of those. I had a +3 scimitar, the ring of wizardry, and stat items (dexterity and int/cha).
4. At mid- to high-levels, how often did you find yourself not using your Swift Action for the round? Currently my plan is to take Arcane Strike to fill in those rounds when I don't need to cast a quickened spell or access the spell pool, but I'm wondering how often that will be. Obviously the less often I have a Swift Action available, the less useful Arcane Strike becomes.
I would say I used my swift action for arcane strike any time I could really unload a full round. It's less good when you had to move to make your attack. There are a lot of swift options for the magus, though. The swift action options are, to my mind, what makes the inquisitor and the magus such compelling classes - they have this enormous advantage over the conventional classes in the action economy.