Gearing - what were they thinking on stock gearing? First is like starting out at 15mph, and 6th is over a hundred. At 65 the thing is just squirelly, feels like it's going to setup a tank slapper at any minute. Probably need to set the rear sag. But seriously, what size is the counter (42rear) and what are you guys doing for 60-65 mph cruising and yet a decent crawl speed for offroad? Did I see 14-44/45 somewhere? The counter must be a 15, no?
***WAIT!! Try Really opening up the bike first like Single or Dual straight through pipes, Open the Air box with drilled holes or Pre filter near the Throttle body opening, and most important put a tuning device such as the JD or comparable unit on and dial in the fuel requirements. After these are done i would venture to say you will have a new out look on how this bike really preforms*** I know i did.
I installed a 14T counter immediately and it works really well. First is low enough for trailing and the bike cruises 72mph at 5K rpm. Over 75 it just feels a little squirelly with dualsport tires.
Stability - does it really need a steering damper or will it settle down once the rear sags a bit more? Like I mentioned, at about 60 if you shake the bars a little man it really starts a shimmey. Kinda scary. Just hold'er steady, eh? My Kawasaki doesn't do that. You have to really try to make it shake - the TE not so much - it's really touchy.
***I see that you already touched on the rear sag, this truly makes a great difference at high speed to set your sag up correctly***
also try raising the front folks a tad in the tree. this helps a little also.
You mean lowering the tubes in the tripleclamp? Lowering the rear and raising the front increases rake lending to high speed stability. I have set the sag and that helped immensely, have not messed with the forks.
Wheels - there are holes drilled but no rimlocks. WTF?? Looks like there's a heavy rubber rim-strip with a tit that pokes thru the rim. And no balance weights. Hmmm... Drill for opposing rim locks to keep balance? Static balance them? Wasn't an issue, but curious what others are doing.
***rim locks are inexpensive if that is a option u would like, balancing should not be to needed unless u really feel bad vibration from the wheels***
I will probably install two rimlocks on my first tire change. Currently balance is not a problem. My buddy with a 310 has the tubliss system and it's pretty out of balance, he gets a good bounce going over 50.
Seat - has that uncomfortable slope forward, and the seat firms up right where you would want to slide back a bit. I can see it's going to need some seat work. Fairly plush though, certainly more than my KTM.
***it looks like people have posted about seat concepts. this is the seat i have on mine. i really must say this is pretty much a must for the money and comfort.***
I met those folks up in Kennedy Meadows a few weeks ago at the ADVRider rally up there. Unforutunately they left before I could stop over to their trailer and try out the seat they had there for the 630. I was bummed. The seat is a bitch though, guess I'll have to pop for the SC seat.
ECU - so my dealer has been fined by the local epa nazi's and won't do ecu tuning any more. First, does it need to be tuned as is (it runs perfectly) and second, if it does how do I get it done? What is iBeat and is it a program and a cable for a laptop that I can buy?
***JD Tuner or unit like it. really not much to say here except that it WORKS!! and its cheap
***
So I've read here. Seems to be the ticket although mine runs really clean from start to over six grand. I'm still holding it back a bit 'till I get just a few more miles on it. I think it hit 6500 last ride. The thing really winds up and things start going by real fast. 
Exhaust - exhaust note is nice but a little quiet. Has anyone de-cat'd them and opened up the internals? And Bill's pipe mod sounds like a great way to go, will contact them directly. What's up with FMF??? A Q4 for my katoom is like $250. Same muffler for a TE is $650 to $750????? What are they thinking???? I suppose a full Leo-V is like $1500 eh?
***now in my opinion its really up to preference on this one and how much u wanna spend. also if u live in US a sparky should probably be something on the list of what to look for in a Exhaust. i personally have the FMF Q4 and it works really well fit and finish are really nice and it sounds great. my friend has the TI single Leo, also a great set up. so pretty much anything to get rid of the cats in the stock mufflers and if you like to save a few LBs then it really up to you cause the power difference once the cats are removed would probably not be sufficient enough to make u choose one pipe over the other. weight and looks, sound PRICE TAG i think are the big thing for the 630.***
I de-cat'd mine, removed the stainless baffle, and ran perforated SS pipe wrapped in glass with the sparky end cap. It's straight through now except for the sparky. I'm really happy with it, a nice mid power bump and more on top than I can use. And it's still as quiet as stock. Runs a lot cooler now too.
Canister vacuum line to the intake - For plugging the brass nipple on the cylinder, do I need something special or just a rubber nipple cap? Does it need to be heat proof? Does it need a clamp?
***i see u have this figured out
***
Skidplate - Any comments on the Hyde one? Are they durable enough more as a rock guard and less so as a bash-plate? The former would be sufficient for me, but curious on opinions. The factory one is like $175 and backordered. I think George's is even more. Ricochet is $90, Hyde $103. Touratech has one but I bet it's $275. I'm leaning to a Hyde polymer one.
***I got uptite... it works, but im sure there are a few that do the same shit hehe***
I got the hyde one, works really well. Did a hundred miles of rocky roads last weekend and heard quite a few clunks and bangs. I see there are at least a couple of nice gouges in the bottom of it. I'm darn glad I put it on there!
The things i wish someone told me right off the bat of buying mine lol
I hope a few things can be had from my experience with the 630 !