Well, I dont really know what to say about assassins creed III...
If you like AC gameplay you will also like AC3 gameplay - but, at least for me, the setting is worse in AC3 now and overall the maps are...let´s say more open.There is more space than in the previous parts, which leads to a lot of ways beeing ran instead of freeclimbed.Also, it seems like the devs got a bit lost in sidestuff.All the village and trading stuff is so extremely optional, Iam about 50% through right now and I haven´t used it at all because it´s just irritating.I liked the economic and trading system way better in the previous ac´s because it was simpler.
Of course there are also nice additions to the gameplay, like the missions on sea - they are FUCKING AWESOME.Will probably be a lot better in AC4, though, so you should not buy it only for the sea battles.
About the missions: They are not very repetitive but the Problem is that you will feel like they are repetitive because most of the missions have been done in a similar way before in the other AC parts - can be very tiring.
What I would say: Not the best part of the series, but still okay.If you like Assassins creed, buy it since it´s off and you are making a good deal.
PS: A mediocre AC game is still a fantastic game compared to most other things available on the market, especially for such a low price.