You are nice and sweet
Usted es agradable.
usted es un amigo agradable
Usted es un niño dulce/tierno. (formal 'you') Tú eres un niño dulce/tierno. (informal 'you')
Mucho gusto en conocerle / conocerles / conocerlo / conocerlos / conocerla / conocerlas (a usted, ustedes) / conocerte / conoceros.Encantado (a) deconocerle / conocerles / conocerlo / conocerlos / conocerla / conocerlas (a usted, ustedes) / conocerte / conoceros.
usted es demasiado bueno (I got this answer from altavista.com)I'd say 'Sos (o eres) un sol'. It's the closest equivalent to 'You're a doll', we wouldn't say 'usted es demasiado bueno', that's a literal translation
Informal: Tú eres simpático. (to a male)Tú eres simpática. (to a female)Formal: Usted es simpático. (to a male)Usted es simpática. (to a female)There are many ways:eres bonitoeres chevereeres agradable
Are you a monster no you're not
"Debe ser agradable lo es" translates to "It must be pleasant, it is."
You are a very agreeable (likeable, nice) person.
You are.
It's pleasant to dream of you.
If you mean "sweet" as in a flavor, "eso es dulce" or perhaps "Que dulce". If you mean something that is caring or emotional, perhaps "Eso es precioso/a", "que amable", "es mono/a", "es suave", or "es rico/a"