In my opinion the LL ligature is not only hard to read; it creates a strong imbalance between the "black" and the "white". A better alternative for a LL ligature is to "stack" one "L" into the other.
Out of the three variations the middle one is the best. But the spacing does look uneven; try to positively track the TA pair. The space between "T" and "A" should be slightly larger than the space between "A" and "L", because of the horizontal stroke on "T". And finally, the "S" needs work; the curves are too irregular.

I don't think your type choice is very Art Nouveau I think you need to incorporate a more florid organic assymetric feel.
Tim

Eduardo, obrigado pelos comentários!

Timd, I agree that it isn't very Art Nouveau, but that's not my intention. It's more of an influence than an attempt to recreate that period's style.

The faces on your link may be more historically accurate, but they're too "caricaturized" for what I need. Thanks for the link, though, has some nice examples.

If you intend to perservere with your design, I recommend the spacing in the third option, but you will need to work on the S start with a more symmetrical shape and develop the smaller top from that and work on the modulation of the stroke. I think that as a logotype it needs something to pull it together to stop it looking like a word, you have a strong shape in the bar of the A, the style of the 19th century would be reinforced by something enclosing the whole or the kind of gradation that an engraver would produce.
Tim

Tim, thanks for your input. I should have been more careful with my words - it's not really a logotype in the normal sense of the word; it's a product name to be applied on packaging. So I'm hoping it'll gain a lot of strenght from the context. The good thing of analyzing it out of such context, I suppose, is that it has to stand by itself and be good just like that.
And you're right that it needs something to make it more of an image and less of a word. Again, thanks. When I have something relevant I'll post a link here (I still have to show it to my boss to see I should keep going or not!) :)