Just for the people who didn't play it yet: yes, AC1 is quite repetitive. But it also gives you the most freedom, a huge countryside between three rather big cities and Masayf of course, the most believable atmosphere, the perfect display of a grey-moral-setting instead of good versus bad, a surprising story and, for me the most important thing, a somewhat dark and sometimes almost scary and mysterious atmoshpere. Also, the most believable combat and the most real challenge. People who want an easy game which does not offer a lot of stuff to think about should probably skip AC1 completely though.
To the OP, you learn counter attacks rather early (along with the short blade and your throwing knives) and from that time on, combat gets a lot more easier. There are no chain kills in AC1, basically the combat is similar to AC2 besides the hidden gun, the smoke bombs and the medicine.