Yes, it’s rare and precious to have one Lama praising and rejoicing at the great Dharma works of another, even though this letter was written some years ago.
I have also checked and found out a fair bit about Tsem Tulku Rinpoche. From the literature, including his biography, he strikes me as an amazingly great Lama himself. Very resilient, always looking forward and from his teachings on Youtube, I can see he is a great teacher, full of live and fun. I also checked and found his blog – blog.tsemtulku.com – that contains a vast diversity of very interesting topics and posts, which, upon, reading and viewing, I find very beautifully Dharmic in content and approach.