When sneaking and using the crossbow, will you instantly be detected by everyone when you shoot someone? A spell will make everyone know your location, but a bow won't. Which one does the corssbow fall into?

Also, does it get the same x3 bonus for sneak as the regular bow, or does it have a very low sneak multiplier like a two-handed weapon?

Cheers.

Spells only reveal you unless you have the Illusion perk silent casting.

Crossbows are silent to an extent. If you shoot someone nearby, anyone else nearby will become instantly alert. Crossbows are silent at range, nearby they let people know someone is there.

As for the latter, I think we won't know until Dawnguard comes out on PC and they can check in the Creation Kit. I've noticed that people I'd normally one shot while sneaking aren't always dying from a single shot with the crossbow, but that might actually be because the bolts do significantly less damage than the best arrows.

Hmm. Sounds like a full stealth crossbow assassin will be harder than a bow assassin.

Crossbows pack a mean punch, and if you take the proper perks in the Archery tree you can fire roughly 30 bolts a minute. The slow reload time is actually not that bad, almost as fast as pulling a bow back all the way, unless you use Zephyr. No contest there. As an archery only character, I've found crossbows to be fantastic.
As for being stealthy, using a crossbow forces you to re-evaluate certain situations. Force you to find an alternative path if you don't want to engage all the enemy, or look for other means to kill them, traps and such. I found it really fun. It forced me to be creative.

As far as I saw, my crossbows produced no more noise than my bow, something I found strange considering how damn loud it sounds to me when they fire

Get the perk that lets you more quicker with a drawn bow. It will allow you to bypass the slow movement when using and reloading the crossbow. It will still load slowly, but you can move quicker and get into some shadows.

As far as the silent part, the actual sound of firing the crossbow wont alert enemies until you hit one. Then they'll just run around going "Who's there?!" until either a] they find you or b] you go back into Hidden mode.

You sure about that? The wiki page said it fires louder than the bow and has a tendency to reveal your position if enemies are close by when you fire it.

I don't think the Crossbow is "loud", but it's probably set to "normal". I doubt it's "silent" like the bow.

Of course, I'm speaking in terms of G.E.C.K. here, I don't know how the CK works.

Crossbows are an AWESOME assassination toy. They are always cocked and ready to fire. No waiting to draw the bow back. Point, click, reload and your ready to rock again. Enhanced versions ignore a signifigant portion of the enemies armor, and you can craft your own elemental dentonating bolts to exploit enemy weaknesses. Just add your poison of choice and its a pure joy to play with. Nor does it draw any more attention then a bow. ya hit some one, others come looking same as always. Mind you i've only 1 rank of stealth and wear some muffled boots, nor do i have any archery perks. Its still one of my favorite toys. An assassin actualy perked to use one will do some wicked, wicked things.

Its a lot of fun when you nail a guy with a paralyze poison and kill them instantly. They die in their original paralyzed position and don't rag doll

The crossbow for me gets only 2x sneak multiplier, but it is still pretty reasonable seeing as it staggers on every shot - compensating for the slow reload, once i get the quickdraw perk that will finalise things and make it better than my daedric bow in every way.

The crossbow is louder then the bow and will put npcs near-by in a higher state of alert, i.e. the steatlh eye will open more. It is still an effective stealth weapon, just not as silent.

I don't think so, from experience it seems exactly the same in terms of detection.

Incorrect but depending on how much you have put into Sneak an Archery perks the Sneak bonus for the CrossBow is exactly the same as for the Bow
as for the difference Between CB and Bow while playing Stealthy the CB is more "Noisy" and enemys seem to be more easy to detect you when using the CB
but CB staggers with every shot and reload is (with Archery perks) quite fast

but range is much less than the bow (the bolts drop much faster than arrows) they do decent damage and gets even better when upgraded
but its supposed to be since CB is meant for short to medium range

Yeah, but don't do it if you intend on raising their corpse with conjuration. Characters that die while paralyzed glitch when raised. They just stand there and do nothing.