Re: AC cos I'm ashamed of saying something nice about Vista
Yup, those were two of the major issues that turned the public against Vista.
Regarding 1), adding UAC was a fine idea on a conceptual level (after all, Linux and MacOS have equivalent features). Where it failed practically was with the OEMs who installed bucketloads of bloatware on their PCs, most (if not all) requiring admin access, triggering UAC in some cases up to 30 times on each boot up (how anyone thought that that was ok is beyond me). Naturally, users hated the new OS and the UAC.
Regarding 2), the 512MB requirement was a concession from MS to (once again) OEMs, who could save a few $ (less than 10, if I remember correctly) per machine and still call it Vista compatible. As much as I understand that MS and large OEMs live in almost symbiosis, this was a bad call.
Another problem were graphics cards of the day. Most PCs at that time had Intel integrated graphics, yet Intel had no GPU capable of driving Vista Aero at the time the then new OS was released (DX9/SM2.0 capability was required). There were parts that had the capability on paper, but in practice (due to horrendous drivers and "shortcuts" made in hardware), none worked. Those users would buy brand spanking new "Vista compatible" laptops and get the ugly as sin Vista Basic GUI instead of what they saw in all of the ads and, whatever they did, they couldn't get it to work. Good luck trying to explain to a non technical person how Aero not working on their brand new, expensive machine was anything but MS's fault.
There were also problems with Nvidia, who was still unprepared at the time of release and whose drivers caused the vast majority of all of Vista's crashes in the first months after release. But whom did the average person blame, Nvidia (who, in the eyes of the broad public, could do no wrong with their drivers, ever) or Windows (whose instability was a meme before that term existed)? Plus there were problems with some older NV parts (at least some FX series GPUs) who had similar HW and SW shortcuts and now didn't work properly with Aero.
So, mix all that together and add the usual "if you want to sound tech savvy, just say that MS is crap" and people were hating on the new OS to no end. Meanwhile, my at the time already vintage single core Athlon64 machine with 1GB RAM and a Radeon 9800Pro ran Vista like a champ, although the OS did take maybe 200MB more out of the RAM than Windows 2000 did when ran on the same machine (Win2000 is a lot lighter on its own, but add GPU and other drivers, with their new .NET control panels, and an AV of the day and the difference was not as drastic).