1. I really appreciate you saying so!
2. I really appreciate your saying so!
(Which one is grammatical?)
We here both sentences a lot. However, the 2nd sentences is grammatical.
http://answers.yahoo.com/question/index?qid=20061123003944AAB2y12
Both sentences are grammatically correct, but they have slightly different structures.
1. "I really appreciate you saying so!" - In this sentence, "you" is the subject of the gerund phrase "saying so". The gerund phrase acts as the direct object of the verb "appreciate".
2. "I really appreciate your saying so!" - In this sentence, "your" is a possessive adjective modifying the gerund phrase "saying so". The gerund phrase still acts as the direct object of the verb "appreciate", but now it is showing ownership or possession.
Both forms are commonly used and convey the same meaning. The choice between them mainly comes down to personal preference and stylistic considerations.