I've had both the Tektro/Cane Creek and the BL-R600 (R400?). The Tektros have a plastic body which is light but I found pretty "hollow" and the horizontal play in the metal lever itself was disappointing. The body was big but possibly too big for me; I didn't feel as though I could get a complete grip. Couple that with the loose lever arm and it was an okay lever for the price but nothing special.

The Shimano R600 (never tried the R400 but they seem similar) I recently got and their quality is really great. The body is metal and solid with the right amount of heft, the hoods feel slightly thicker, and the design allows my hand to get a comfortable, firmer grip. The metal levers are nicely polished with little lateral play. Whereas the Tektros felt unnecessarily big, the Shimanos were compact and of distinguishably better quality. I do wish they had the quick-release mechanism. They do cost almost 3X the price but they seem to be pretty cheap on eBay though. If you like the Shimano Aero design from the 80's (105, 600, etc.) then the R600 will not disappoint.

I also want to throw out Gran Compe levers too. I found that the higher quality stuff from Dia Compe was surprisingly good. I have Aero Gran Compe levers and the hood material is phenomenal while the body is solid, maybe a bit chunky. They started the whole spring in the lever part design I believe.

The SRAM don't look CV at all... look like brifters without the "-ifters" part.