Ok, so I had a good opportunity today to really play around with the machine A600GS. I even managed to do a 3.9 set up thanks to iowtheme's useful video tutorials on Youtube on how to set up a workbench on a 1200NG.
I tested out a few games too both as ADF files and also as WHDload installs within 3.9 and I found the following games would stutter during gameplay:
Pang (on Title screen and on interval screens)
R-Type 2 (runs at a really slow framerate in general)
St Dragon (starts ok but gets slow in places)
Chaos Engine (similar to Pang, slowdown in the music on title and character selection screen) but once in game you are fine.
Space Harrier was a little sluggish too.
The same thing happens on Amibench too despite putting these in the programs folder as suggested.
The JIT emulation setting can either make the game better or worse depending on the game from the above tests.
It kind of reminded me of an issue I used to have when I owned a Sam 460, but luckily that version of E-UAE had a frameskip that you could then tailor to each game.
I honestly think some form of frame skipping setting and greater customisation of the emulation package within the menus would be welcome. I am saying this constructively because I actually think the A600GS is a good product and want it to succeed.
In general I was more impressed with my purchase after getting OS3.9 set up. I have even ordered the latest OS 3.2 to set up when it arrives.
Hi outrun1978,
After reading your post, I thought I'd give some of those a try myself. I've started with Pang.
On a Custom Amiga 1200 setup with 2 MB of Chip and 8 MB of Fast, CPU 030 maximum speed, and JIT activated, Pang (WHD-Load) stutters on the titlescreen. However, when I turned off JIT on the same setup, the stutter disappeared. Please give that a try to see if it works on your setup. Would be interesting to know.
Running Pang as an ADF with an Amiga 500 setup 512 KB + 512 KB gives a smooth experience here. There is no JIT activated there either.
Also tried Chaos Engine with no JIT as WHD-Load with the same setup. No stutter here.
R-Type 2 works without slowdowns as well. Just tested.
From these tests, it looks like having JIT activated can slow down some games.
I tried degrading the system to Amiga 1200 / 020 / 2 MB Chip 8 MB Fast / 14 MHz - No JIT. Tried running Pang (WHD-Load) and it worked great.

Now I changed the system to a 68040 / 2 MB Chip 8 MB Fast / Maximum speed with JIT, and the stutter re-appeared in Pang.
Running firmware 46.2.1098.
Update:
Activated JIT on 68030 setup, but sat max MHz to 25... stutter disappeared in Pang with JIT... Maybe this is the problem? Having CPU Speed set to maximum? Hope someone can give this a try too.