I've been reading over SR4 for the last couple of days, having been playing since SR1, I've found that there are a lot of assumptions about the "way things work" that I'm having to consciously overcome.
When I was making up a character to try the system out, one of the first examples of this was the smartgun. The current ruleset has things working very differently. There is no +1 instead of +2 modifier for using goggles instead of cyberware, and in fact from what I can see, there is no compelling reason to have the cyberware version at all (except for the fact it can't easily be taken off you)
You can get a smartgun, you can wirelessly link it to your commlink (or skinlink it to your commlink), then have your commlink link to a pair of glasses that have lowlight, thermo, vision link and smartlink all in one. From what I can see, you don't even need a neural net/paste etc to get a setup like this. It just takes some non cyberware toys, and a bit of cash.
The question about it though, is in regards to the free actions and the like that smartlinks give you. The ability to eject the clip, change firing modes etc, are all listed as free actions if you have a smartlink. But how is this a free action if you don't have a neural interface of some kind? Even if you don't manually eject the clip from your gun, without a neural net/datajack etc, you'd have to manually fiddle with your commlink to issue a command. But that doesn't seem like it should be a free action. So am I missing something and you actually need some sort of neural interface to access a smartlinked gun?