To be honest, I have never liked them; they're silly.
Very much a product of the 60's. Like the Gorn, they just about work in TOS, but would look ridiculous post TNG.
One of those races, like the Tholians, that have been mentioned quite a bit, but rarely seen. And there's a good reason for that.
Some alien races in Star Trek have really stuck, with fans constantly wanting to see more; many have even become household names (Klingon, Vulcan etc.). Yet for every one of these, there are several other races in the Star Trek canon which have just been flops; races that never sparked any interest and that nobody really cares about. The Remans and the Xindi are probably the latest such example, but there are dozens of others, some of which even fans have trouble placing. Most of the inhabitants of the Delta Quadrant fall into this category.
Having said that, Dr. Henglar on the excellent fan series Hidden Frontier is a Tellorite, he even had a spin-off audio series playing the title character!