I actually get what he meant about the GGT being "too versatile." It's not a complaint that it will take all the different battery combinations, but that it can be a hassle to do so, especially on the fly what with adding and removing pieces and adjusting the spring. With a regular mod, the battery choice is more limited, but that means it's never a hassle to change batts. In short, the Transformer tried to do it all, but in doing so, it got complicated. I've had stuff like that before, items that were supposed to be versatile but were such a pain to change that I only ever used them in one way.
On the other hand, the TS does it all while remaining very simple to use; at most, only one piece ever has to be removed, and that's only for the smallest of batts.
I probably would have been fine with a Transformer (well, except for the 901 part, because I don't like using adapters). I don't have a lot of mods, so I don't have a huge collection of different types of batts to use. My GGTS has had an 18650 in it since 30 seconds after it arrived, and it will probably stay like that. But if I had lots of different batts from different mods, and I was told that I could use any of them with the Transformer, I can see how it might be aggravating to have to fiddle with it to get different batts to work.
Mostly, I'm glad that Imeo didn't seem 100% satisfied with the Transformer, because it led to the GGTS, and I'm very happy with my TS. I think if Grimm had gotten to review the TS instead, he would have seen the versatility as a virtue instead of a hassle.