Horizon may be better than the people who used to service GM stuff, but not by much.
I have a V12 and a V3, and love GM speedos, but man do I hate horizon service. Their slow as dirt, and some of them are idiots. I sent my V12 into them to have the brakes checked out, and the thing came back to me with the case popped open and uncloseable because they got dirt or something on the adhesive side of the label, and burn marks on the case that weren't there when I sent it in. Basically, when I opened the box they sent it back in, the speedo was a mess!
Their take on it when I called....."it was like that when you sent it in". Yeah, okay!
So now I take dated detail photos of anything I send to horizonhobbies. Not taking anymore chances with them.
GM's new speedo looks great. I'm not too fond of the external programing thing though. The small size is cool, but that power cap that Masami had on his 1/12 scale car was HUGE! Almost as big as the speedo. I hope thats not the size that will be required to run the speedo!