could'nt say
Does Windows 10 perform well on Windows 7 era hardware?
with a 2011 i7-2600 and a 2009 intel xm-25 ssd, Yes it does.
Yeah SSD. What about with a 5400rpm HDD? SSD's were not at all mainstream back in 2011. You're using a rather high-end configuration as an example. I'm taking about Core 2 Duos which were mainstream in '09 when Windows 7 was released. Intel made such a giant leap with its CPUs around that time that every subsequent generation has brought minor improvements. More along the lines of additional capabilities but really in terms of raw performance. GPUs are were the performance improvements have been dramatic over the last decade. AMD by then was years behind. In the early 2000s AMD had been on par with Intel and in some cases surpassed Intel's performance much like Nvidia had no answer to ATI's R300 for a couple of years.
XP era spanned a long time. Core 2 Duo was released near the end of that so pretty much peak XP performance. Early XP with Pentium 3 and 4, not so much. Something like a Core 2 Duo E8400 or Core 2 Quad Q9550 actually handled Windows 7 very well particularly if one pairs it with an SSD. Moreso with a discrete GPU for Aero.
A large part of the SSD push actually came about because Intel processors were fast enough that the storage subsystem became the biggest bottleneck for most people's usage. If one has a PC with HDD from 2011, installing an SSD on it is like a breath of fresh air. I bought my first SSD in 2009, iirc. By 2011, all my computers had at least a 120GB SSD for operating system and programs. Power efficiency became a bigger focus for Intel rather than pure performance. I had low-power 1.8GHz Celeron 1037U Ivy Bridge Mini-ITX builds with 128GB SSD on Windows 7 handling basic computing duties just fine.
I don't have extensive experience with Windows 10 but the few laptops I've dealt wih (ULV processors so likely still slower than Core i5-2500) don't appear to run significantly slower than Windows 7, again, as long as the build has a decent SSD and at least 4GB RAM.
P.S. Just checked PassMark. A Core 2 Duo E8400 actually scores higher in single-core than the Core M-5Y31 found in some rMB and ultrabooks.