I believe this was posted elsewhere, but I have some concerns with the flavor of the class. This is most certainly a personal thing, and I don't expect everyone to agree with me. However, for me, the idea of a melee combatant who blends the art of magic with that to become adept at both, but masters neither does not "jive" with wearing anything more than light armor. This is especially true, for me, if you're creating a class that is strictly to use a 1 hander and a free hand with 3/4 BAB. This isn't supposed to be an "arcane paladin." I'd like to see the armor proficiencies removed in favor of magically enhanced, perhaps insight based, ac. Int as an insight or deflection bonus to ac while wearing no armor, or something to that effect.
Saves
I would also swap the fort and reflex saves; somehow the idea of a 3/4 BAB d8 melee class with a high fort save instead of high reflex just doesn't "jive" either.
BAB
Surprisingly, I'm alright with the 3/4 BAB and d8. It's somewhere in between a caster and a full fighter or paladin, and fits the flavor quite nicely. With feats such as arcane strike, weapon focus and weapon specialization, and the arcane accuracy magus arcana, accuracy doesn't seem like it would be a big issue.
Spells
A spell list of its own makes sense, and I'm sure with the final version, there will be plenty of delicious touch spells added on from the new book. However, what's with the PREPARED CASTING?!?!? I mean, I suppose it's not a big deal, but it is a point of concern for me.
Abilities
Spellstrike needs to be reworked. Jason has clarified in various posts now that it does not mean you get to cast and attack in the same round. You have to cast the touch spell, and you can then choose to deliver it through your weapon in the next round. Essentially you are holding the spell until the next round and then you may deliver it while attacking. Aside from attacks of opportunity, and some other very specific rare instances, I do not see the point in this ability. It should be reworked to be similar to the Duskblade arcane channeling ability from the 3.5 PHBII. Because the magus pretty much requires a one handed weapon and a free hand, an ability similar to the duskblade's arcane channeling would not be anywhere near as broken as it was in 3.5 since you wouldn't be able to channel while TWF. Keep it limited to touch spells obviously.
Spell Combat is unique, and enjoyable conceptually. The increased penalty to the concentration check makes sense. However, mathematically, at lower to mid levels, the ability is just not worth it. I believe it was Cartigan who pointed out that you essentially take a -4 to attack rolls for a 50% chance to cast a spell while you're attacking.
Also, as a little aside here, it seems like combat casting is pretty much a requirement for this class. Why not just give it to them for free? Feat taxes are lame. I suppose I could make the same comment for arcane strike. And sure, the magus arcana "concentrate" solves this a little bit, however it's once per day.
Now then, Magus Arcana. I think the Bonus feat thing needs to be rolled into magus arcana, and the levels you get magus arcana should be adjusted accordingly. That would be good for versatility and personal flavor and customization for each magus. I think the Broad Study Magus Arcana needs to add a line that lets you add touch spells from other arcane spell caster lists to your own list so that way it is actually useful for a non-multiclass magus. A higher level arcana that lets you replace either strength bonus to attack or damage with your int bonus would be cool, though balance wise I'm not sure how feasible that is. It would get rid of a lot of the MAD issues that I see arising since this is a class that will not have as high of an int bonus as a wizard due to the melee needs of dex, str and con. An arcane accuracy but for weapon damage would be nice as well. That or some magus arcana that improves the way arcane strike works, and/or makes it so arcane strike is a free action. Critical Strike needs to not be a swift action or the aforementioned changes to arcane strike need to happen. A magus arcana that allows you to add one wizard spell to your list each time you take it would be cool as well. A magus arcana that gives spell resistance, one that allows increased caster level to overcome SR when casting spells with spellstrike or spell combat similar to the duskblade ability, and one that allows an increase in the dc of the spell cast with spellstrike and spell combat; these would all be good ideas. All of this would create a system of versatility. No two magi would be the same.
Arcane Weapon is quite good as is, however I'm curious as to whether it's supposed to act in the same way as a wizard's bonded weapon in that you can enchant it as if you had the appropriate item creation feats. I realize that it does not say this in the text, but the text does make mention of the concentration check so I thought I'd verify.
Weapon Bond is also fine as is, however my concern is that it's not worthy of being a 19th level ability. Yes, I understand that it makes you immune to disarm, and you will constantly know where your weapon is at all times, however, how often does disarm really happen? Often enough to warrant an ability like this? Sure. 19th level? Not so sure. I feel like other classes have cooler higher level abilities like DR, Mass suggestion, Gate, Great Hex, Great Quarry, and Empty Body.