ASCIS 2160 to Kayano

I had to get a replacement pair for my Ascis 2160 which has clocked just over 300miles and has lost most of it's thread on the soles and was sqeaking on concrete when I run! I remember trying this pair for the first time, and it felt brilliant in that I didn't feel it at all at first go, it may be because my previous pair was 2140, so maybe little change. I've now got a new Kayano 17, and tried it yesterday. The first few miles felt like my feet and ankle was a little heavy not due to the weight of the shoes. The run felt more difficult, and I wondered if it was the heat (was 22C and sunny), or the fact I had not run for a few days, or could it be the shoes?

I've heard mostly good reports about the Kayano's, but also some people seem  not to like it. I've got very flat overpronating feet. I'm keeping an open mind about my Kayano, but wondered if I should go back to the 21xx model. I appreciate it's a personal preference thing, but I wonder if anyone else had any similar experiences to share?