Ditto - I jumped on board the Apple wagon in the early 2000's and have couple of iMac's, iBook and a fair few iPods, iPhone (best gadget ever??) etc. Would never go back and I have converted a few - all the same as me, would never go back. Sure they are expensive but well worth it.
In terms of where to buy - official site as good as anywhere, don't think there are real discounts to be had anywhere and at least from there you know you are getting the latest version.