Yes, they are lovely.
My GD was just learning to write, still needing to ask how to spell even short words and some help with letters, when she produced a sheet of paper decorated with the waste bits from around stickers. It read 'I love my Gran'. It's safely stored away. Another time, she and I were walking, hand in hand, around the garden. She was still pre-school age, her parents had separated and her dad had brought her to stay for a couple of days. As we walked she said 'I like it here with you, Gran'. I can't tell you how that made me feel.
A friend once told me that you're as passionate about your GCs as about your own children. I'd say more so.