The thing is, MS could have made they SP3 a few millimeters thicker and achieved the equivelant performance of the SP2. Instead, MS chose to chase the iPad form factor and as a result significantly hobbled the performance. No one expects a tablet to compete with a gaming laptop, just like no one expects a gaming laptop to compete with a gaming desktop. But, the SP3's performance could have been better if not for a poor design decision.
IMO MS is chasing the desires of most users not the high end gamer in choosing thinner and lighter. The performance will be very good for most users. you can do a lot with it and never see throttling.
I don't see throttling when browsing the web, doing office work, watching HD videos (either streamed or from USB Disk on the same docking station I have two DisplayLink monitors running off of plus my wired Ethernet connection, kybd & mouse). I occasionally play mahjong but haven't tried it yet
sometimes I get so many tabs open in a browser window I open another one or two or use both desktop and metro.
I don't see throttling when running Sysmark for 4 hours, PassMark, or PCMark (Home, work, or Creative) benchmarks. I do see throttling running 3DMark, or the Intel XTU tests.
I think its PCMark that does a 25000 row Matrix calculation in a spreadsheet. They do image manipulation... id call it light but likely representative of what most users do. These benchmarks are designed to evaluate systems for use with typical use cases.
It would be nice if MS can tune the firmware to get closer to SP2 performance on these tougher workloads but I never bought a Surface Pro until the SP3 because IMO it was to thick. As a tablet device I found the Surface 2 to be quite good for web browsing, video watching, playing Mahjong and light office work. The SP3 is much faster and the S2 was in the same ballpark as iPad Air and Galaxy Note 10.1 2014.
Certainly there are websites and Google apps that don't work well... I see that as mostly their problem and have pretty much shutdown anything with those.