Just a general query, what is the block size that you usually work with? When I started to learn to quilt, the instructor was keen to use 12" as the standard sized block and this is the size I use. However, I have noticed that there are quite a number of quilts where it appears the blocks appear much larger than 12" or is it my eyes that are playing tricks on me? Does it actually matter if they are bigger/smaller or is it just preference? Thank you for sharing.

It is preference.. I like 12" blocks for some quilts, but other's IMHO a 6" blocks looks nicer. I guess it depends on the pattern and overall size of the quilt.
I have seen some blocks that are 24"+... too :D:D:D

I've been doing 9 inch blocks lately. They're big enough to give reasonably speedy progress without seeming overwhelming.

Experiment with different blocks in different sizes to see what looks good to you. :)

First, I will consider the purpose of the quilt. In making charity quilts [my biggest focus], the larger the block - the faster the sewing just love that 10 minute block [learned about it here on the QB]. It looks terrific with the variety of centers and pieces really fast into a scrappy or somewhat planned design.
The 12" blocks [especially the Quilt in the Day series] are another one of my favorites for the size and instructions.
For my own "play" I like paper piecing. Also, using my scraps how did so many accumulate.....I am cutting up bits for the 1.5" square [postage stamps],1.5" and 1.5" x 2.5" which makes a 5.5" block in the Bonnie Hunter manner. Remember the "leaders and enders". Those may be forever blocks tedious yet fun. Who needs therapy when there is quilting? Thanks for letting me express my some opinions.

12" blocks are the usual for me..next size is 9 inch.

For small quilts I prefer smaller blocks - or large blocks with lots of small pieces; for large quilts I use larger blocks. It's a matter of scale.

Thank you so much for your feedback/suggestions. It really makes a difference. I thought that there was a set rule but wasn't sure.

I usually do 12 inch finished blocks, but also like 9 inch finished.

7" and 9" finished are my usual sizes
Have done some at 4" and another at 17". Like others have said - it depends on the pattern.
My rule is - larger blocks, i.e. 12" and up need more complicated designs