Ah the agony of decision
I've never used the scoring option on mine (and probably wouldn't have bought it except it was part of the package deal) - again if you are like Charlie and do a lot of plywood or (especially) melamine pieces I suspect it would be invaluable. For solid wood it doesn't seem worth the bother and is currently another part to break eventually. I may someday change my tune if I end up doing more cabinet work
For the dado - again will you use it? You can't add it later so.. it might well be worth considering just so you don't regret not having it later.. maybe..
Even if you don't get it DO get one of the wooden (plywood) "dado inserts" to use as a template for making a zero clearance insert. To say the design of the insert is complicated is vastly understating it so having a template to work from is quite convenient. The stock plastic insert has a pretty wide gap in order to allow for adequate airflow but is a pain if you're cutting small stuff because it tends to get sucked in. I made a handful of inserts out of poplar (any reasonably stable and easy to work wood would work) and they weren't that hard to do, but working from the platic piece would have been a bit harder.
On the down side, shaper cutters are generally pretty expensive, though - much more so than router bits.
I actually didn't find that quite as true as I was afraid it would be. It was both true and not
For individualy insert cutters they are pretty much competitive to router cutters; I've bought felder insert cutters in the $20-30 range and many other manufacturers seem close. If you want a variety of molding profiles its a reasonably cost effective way to go. On the flip side the cutter head that the inserts go into was a bit more up front, and the heavier profile cutters for door frames, etc.. are also quite a bit more. Also you can really only do profile cuts with it so you'd still probably want something for router type cuts. Double check the size of the shaft, I think? it defaults to 3/4" and ships with a 30mm sleeve (I also bought a 1 1/4" sleeve so I could use NA cutter heads easier) - if you get something compatible with the 30mm you should be ok for most euro cutter heads (side note one of the collars for the initial 30mm sleeve I got was a bit to tight to actually get on perhaps as a result of a ding in shipping, felder shipped me a replacement no questions). Largely depends on the type of flat work you want to do; for cutting molding profiles - the tilting head is pretty useful to have (especially combined with the sliding table for cutting end profiles). If you have room a (used) standalone shaper is probably cheaper and perhaps more flexible in use, but the hammer product is quite compact since its part of the saw and has most all of the features you'd want in a nice shaper. I admit to also not having used mine as much as I'd have wanted :| Also note you have to store the dust collection hood/fence somewhere when its not in use.
An extra flip stop on the outrigger fence was one of my first post-machine-purchase purchases. Having two flip stops was really nice for cutting frames or rail+stile to length. Obviously an easy after purchase as well but something that imho most folks will end up liking if they get it.
I believe you're looking at the 79" slider - the longer slider is definitely useful for solid wood for straight line ripping if you work with rough lumber of size very much.
The ripping shoe is just some bent sheet metal (heavy sheet metal) and imho not worth the money I paid, it works "ok" but it sits a bit to far from the edge of the slider for much of my use and it would be pretty easy to fabricate a functionally similar but nicer piece.
The manual hold down clamp is substantial and probably worth the money with a couple of caveats. Be careful with the "nut" that goes into the slider slot, I cross threaded and stripped on hole on mine turning by hand - fortunately its just a straight piece of iron with two holes in it so was easy to make a new one out of a piece of mild steel with a hacksaw, file, drill press and hand tap. The plastic foot slips a bit and tends to mark workpieces, also easily solved by putting a piece of medium weight leather between it and the wood.