Personally, I'm really enjoying the new Game Grumps. Yeah, the initial shock of Jon suddenly dropping out is still wearing off (and was a really big surprise considering both he and Arin mentioned in some earlier episodes that they had gone through the process of legally becoming business partners and co-owners of the "company" of Game Grumps,) but Dan and Arin have a great dynamic together than I can only see improving, possibly becoming as refined as the chemistry Jon and Arin had. Also, it's nice to see some actual GOOD gameplay from on Grumps once in awhile, and Dan is kicking some ass with SMB2 and Punch-Out!!.
As for Steam Train: it's rough, but it has had a few amusing moments for me. Ross and Dan don't play off of each other as well as Dan does with Arin, but the show is just starting out and I don't think they've really had the chance to make it their own yet. I see potential though, once they get more comfortable with it.