Have had most of the others but got this yesterday. It is a bit weird to start with and it's the same gameplay (go around and takeover the whole map, go up towers etc) but still pretty enjoyable.
Yeah, got it around the release date. I loved 3 and couldn't get on with 4 as it was a bit samey but I'm really enjoying this, the setting helps a lot. Being able to dip in and out at your own pace is good, I have little 20-min blasts of it now and then, just finished the second of the three main regions.
No, only had 2 and 3 and borrowed 4 for a very brief time. Didn't get on massively with 2 either, although that's a lot of people's favourite as it's so sparse.