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I'm practically at square one on 40K experience, and working on an infiltrating SM army  (see "Noobalicious..." post in lists if you need to).  From what Ive been reading though, tac squad heavy armies without meteors, exploding backpacks, or iron shoe boxes to zip them across the field end up being shot/torn to little +3 strips of armor.  I love the fluff i have in my noggin for these guys, and the theme is entertaining, but if See But Don't Be Seen leads to a deep, dark hole of losing streaks, me thinks I should reconsider what Im going for. 
I DO realize that I wont always be able to infiltrate, and I can deal with that.  But when I can infiltrate, will it be of any significant benefit, or just a "Huh, neat" moment that leads to an invariably painful debriefing and countless man hours picking gene seeds out of craters?
Drop Pods just cost too damn much!!!

Infiltrating can be cool. You will be better served with smaller units, since you can hide better, and thus get closer.

You get the advantage of setting up after you opponent is finished.

But also realize that it not what you want against certain lists. I doubt you really want to get closer to the Nids or Orks....

But you can also just overload a side. Eh, it sounds like fun.

If you're doing a shooty infiltrating army, this is the crux of the advantage. You get to place your guns after your opponent has put out all your targets, and can maximize your fire lanes, while minimizing exposure to assault units.

Marines have the best basic troop option in the game, so I have a hard time imagining that you'd go far wrong by taking a bunch tactical marines. That said, I think that it would be important to maintain a strong counter assault element (assault marines spring to mind), the traditional breakdown being 70/30 shooting/assault.

Case in point, the Alpha legion (chaosy infiltrators) are one of the stronger lists from a thoroughly broken codex, so if you start to have winning issues, you could look at going the chaos route (or even starting there...). A strong combination is the "cleanse and purify" along with "see but don't be seen" as it allows you to put out more firepower on the move at close range. That type of army may be better served and accomplished with a chaos list though.

Overall, it's your choice and I think shooty infiltrating marines are doable, if you don't expect to win gladiator tournies or the UKGT with the list.

cheers

Most of the time if you have to pay 3pts for infiltrate you'd do better buying 20% more guys and just walking.

At 1pt per model it's a bargain, hence why Alpha Legion is a very popular Chaos army.

Also take into account that the Alpha Legion list may not be available as such in six months; many rumors (note: I said rumors) abound that there will be a new, simpler Chaos 'dex coming out Septemberish.

I'm not saying it's definitely going away, but be wary.

Hm, not much interest in chaos to be honest.  I started playing around with a Night Lords theme a couple years back, which ended the moment i bought a box of Raptors and saw just how cruel metal models can be.  Plus, Im still working on greenstuffing rags, Im not ready for countless eyeballs, gaping wounds, extra limbs and distended jaws, gruesomely cool they may be.
A bit of a neutral variety of enthusiasm so far on See But... armies.  Truthfully, shooty was what I was thinking at first, but I dont know if a squad of 8 marines with a PF sarge, plasma gun and h. bolter qualifies as "shooty".  Cleanse and Purify does sound fun, probably something Ill have to try as a tweak when things get up and running.

Maybe my marines are just feeling insecure?  Should include a librarian in my list for counseling the lil snots...

You mentioned why all infiltrating tends to end badly (the games that don't allow infiltration)

However, using a couple of squads of your core as infiltrators can be very successful. Especially when combined with other elements of the Marine List. Terminators and Drop-poding dreads are the two that can really move nicely to help support an advanced force.

I've seen Infiltrating Mult-Melta Devestator squads used to produce some devestating effects. 24" of no-go goodness can help carve out interesting tactical effects.

Even against assaulty armies...once you get to know how fast your opponents move...you can infiltrate very nicely to get rapid fire off and coordinate your assults squads into weakened units.
I love deploying 20" away from an opponent that has 18" assault range....and then blasting them as they come up short (since most things that are fast in this game also tend to be flimsy)