Yeah, the option to hide store was removed. I liked it as well, but that's the way it is now. To be honest, it's not really annoying. Store button is there, but if you never click it, all you'll see is that button and nothing else. Not really annoying unlike in most other AV's where you get "fake" buttons everywhere that just show what you can get if you buy a full version but they don't really do anything when you're a free user. I frankly don't mind it since i've started using avast! 2015 BETA back in august. I think you'll forget about it as well in no time.
The reson why Web Shield no scans so much stuff is because so many sites are using HTTPS by default now (loads of forums, blogs, Facebook, everything from Google etc). And old HTTP scanner was unable to scan any of that. That's why they incorporated HTTPS scanner, so they can also scan those connections. Before HTTPS scanning was added, any encrypted page skipped the Web Shield and was only scanned by the File System Shield once connection alreagy got through the browser. Web Shield scans it befor it even enters the browser. That's why it's better to scan stuff before it enters browser to prevent exploits and stuff.
As for memory usage, it can temporarely increase, because it has to scan more stuff now. Plus decrypting HTTPS connections also requires memory, though i don't think that should be the case, because HTTPS has to be decrypted before it can be used and that is always done either by browser itself or avast!. So that shouldn't make any difference i think.