My views on the POTENTIAL uses of connectivity.
Being able to pull a log of what shots are being made, features started/completed etc.
This will be provide great feedback as to what the people playing the machine are actually shooting for. As
@Neil McRae said earlier, lots of games have benefitted from code updates after players have discovered bugs or exploits, or even suggested completely new modes/features. This is surely a massive bonus in the development and design of future games, improving the chances of a game being released closer to complete.
I often go through the audits to see what modes I am completing more often than others, meaning I can make informed decisions as to which will benefit me more.
Being able to download updates without the need for memory stick
Not a huge improvement, but still an improvement - and likely to be optional anyway.
Logging 'achievements'
Take it or leave it, but I suspect more people will be taking it than they think they will. You only have to look at the high score thread here, or the talk about reaching Valinor, or any other wizard mode, to see how much people are invested in reaching these. This will make it not only easier for you to display this (I'm amazed at how many people feel the need to share their meals on Instagram or Twitter FFS) people will be doing this.
It will also steer you towards areas of the game that you may not even know existed, let alone achieved.
Downloading DLC
To me this is my biggest fear. That there will be modes that can only be played if you subscribe and/or pay for them. Although this will be possible, there is yet no evidence that this is the intention.
Identifying non-Stern mods/Hacks
It's already in the T&Cs when you download latest code from the Stern website that you won't add anything non-approved without written authorisation from Stern. This would allow them to identify if you did.
Again this could be a concern. Could Stern really brick your machine if you installed non-Stern code? Would they? Or would it just invalidate any guarantee, regardless of whether the add-on caused the problem.
If you want to add a non-Stern shaker motor, because it is cheaper, that's the risk you take. You can hardly expect Stern to honour a warranty if you've caused it by adding something non-Stern and it blows a node board.
No Cleland code, no hacked modes, no non-Stern mods, could cause some people consternation, but is hardly the end of the world.
Comparing Highscores
I think everyone here can agree that there is no way of comparing scores on different physical games, but people still do. Highscore thread here, Pinside highscores, etc.
What this could do is allow only scores displayed which are played on a certain set-up (Factory, Hard, Easy, whatever).
At the moment all of peoples views are based on pure speculation. I doubt everything that people have suggested will be implemented, and likely things that haven't even been thought about yet will.
The cost is a red herring for new games - cost is based on what Stern (or any other manufacturer) think they can charge and still maximise their supply.
The cost to add to an old game is also irrelevant - if you don't want it there's no need for you pay and fit it.