I've got a late 2011 at home, as well as a mid-2012 at work, and yeah, it's definitely worth upgrading. High Sierra runs great on it, and with that i7, you should be able to continue to use it for quite some time.
That said, Apple made a decision "for you" that you should be aware of. With Sierra, Apple forced the OS to reserve 1.5GB RAM (the amount can vary depending on the model) for video, in order to properly support 4K external displays. So, if you have 4GB RAM, you're actually only left with 2.5GB, and your system will be sluggish (and there's no setting for adjusting that on most models).
The official word for RAM on that generation of MBP's is 8GB RAM supported. However, there are lots of accounts on the Internet of folks successfully upgrading to 16GB RAM with no issues, and I can say that I have done so myself and am entirely happy with it. If your work is RAM-intensive, it's well worth the extra few bucks (Euros, name your currency) to go up to 16GB.
I also just replaced the old hard drive with a 500GB SSD on my home laptop, and I would recommend that to anyone, the boot/load performance boost is great. You'll need an external connector/bay for cloning your old drive to the new one, and you can clone with the built-in drive tool, or use a third-party app like Super Duper. You may also want to consider upgrading the file system to APFS when you're done, so that you can take advantage of the new features there.
Bottom line: Go for it! You'll keep that thing blazing for years.