upgraded my 2011 and 2012 MBPs 2 months ago with OS Sierra - works very fine, no problems at all.
For me, they seem even to be faster on Sierra.
Using SSDs since years, having upgraded the RAM (8 or 16 GB) both MBP feel like new machines.
Works very fast and smooth.
Be aware of the fact, that after switching to Sierra your system will work for many hours depending on quantity of data - maybe even a whole day - as hell.
Don´t be desperated - this is normal and will stop once this initial reorganisation of the system has been finished.
2009 and 2010 MBPs are limited to ElCapitan. But they run flawlessly with ElCap...