El Capitan supports all Macs introduced in 2009 or later, and some models introduced in 2007 and 2008* **
* Not including its very much capable but artificially crippled Mac Pro 1,1
** ...unless you hack the boot loader
These websites that are getting all panicky over content blockers are waaaaay overreacting. Apple didn't build ad blockers into Safari, and so users have to go out of their way to find an app, make sure it's not a piece of junk and that it'll do what they want it to do. Ad blockers have been available for the desktop for years, and the internet has survived. Perhaps the best middle ground is for websites to politely ask users to allow ads, and they better be tasteful...
What's with the neglect? This is classic Apple, ignore the lesser product and then choke it off altogether because nobody wants to buy last year's products at inflated prices. The mini isn't competing with the 6 Plus, but it's being treated like a cannibal. For me, the Air is too big for a tablet and the Plus is too big for a phone. Without the mini, guess what I'm buying? Nothing. I'm sticking with my old one until they come to their senses. Would they rather I buy...
The Macbook is for people who want an iPad with a keyboard running OS X. At least that's why I'm buying one. I plan on never plugging anything into it except the power cable, just like I do on my iPad.
They all slow down over time. That's how they get you to buy a new one. I'm being stubborn as my 1st gen iPad Mini grinds to a halt with each iOS8 update. Most of the time it's simple things like text entry lagging that absolutely must be by design. Planned obsolescence.