Sorry, won't help a bit. As Doug said, commerical is a visual rating. As far as general IFR flying, it depends on what you consider benifits.
If you are asking in reference to what airlines will think of you having that experience, it probably won't amount to much. Once you get the FD programmed, using it is brainless, you follow the command bars. Programming it can be confusing for some, so experience with the model that the airline uses might help you personally after you get hired, but it won't make a difference for the interview. The problem with that Arrow's FD will be that it's not the same model that any airline will use, so you won't get the benifit of knowing how to program it.
If you want to keep your basic instrument skills sharp, it will be a detriment.
If you want to be a safe single pilot instrument flyer, then it is the next best thing to an autopilot.
It all depends on what you want to get out of it.