Started out skating 7.75's. Started skating 8's a year or so later, and it felt pretty good so I stuck with 8's for the longest time. Then one day I was getting a new set of trucks because the other set I had cracked at the hanger, and the only Indys the shop had left were 149s. It was either either buy 149's, buy a set of 8 inch ventures or 8 inch silvers, or wait two weeks for the new shipment of indys to get to them. Being the impatient person that I am, I decided to just get the 149s instead of waiting or buying some trucks that I'm not down with. Because of that, it pretty much forced me up to an 8.25 since 149's on a 8 would just feel too weird, but it didn't really matter much to me. Took me a while to get used to but after i got used to them they started feeling pretty good. I rode 8.25's for a lil bit, then one day at the same local shop I went to go buy a new deck, and they didn't have any 8.25s in stock, just a lot of 8's and under, a few 8.125's, and one 8.5. Since I had 149's, I didn't really have much of a choice so I got the 8.5.
I remember hating it at first, it felt so big. Didn't feel comfortable at all. But three or four sessions in I started to like it, and over time I liked the feel of it more and more, and now 8.5 is the size I've stuck with for the past 2 or so years. Now if I ride anything under 8.5 it feels weird. I've been kinda wanting to set up a 7.75 deck lately though, just for the hell of it. Kinda just as an experiment to see how long it would take me to get used to a thinner board again.
As for flip tricks being harder, it doesn't really effect my flip tricks at all. I can still do pretty decently popped kickflips, and I could still throw a double flip out here or there. The one thing I did notice though is that the wider the board the harder I had to work to get decent sized ollies. Other than that though everything pretty much stayed the same.