Whoa, you're up early!
I would spell check it (even though I am quite unlikely to comment "beautiful" on somebody's photos :D). I am still spell-checking some more complex words where I am not fully sure of spelling or meaning, because that helps also me to increase my vocabulary. And at least it shows some respect to the person to whom I am talking.

soo, i also want to ask that what if a prety girl -in terms of physical appearence- would have commented on ur pics with that corrupted usage of english, how would u feel? Bad? My answer would be no, in my point of view, it just depends on what she tries to say, and whether i interested in her, thats all..

I always spell-check if I don't know how the word is spelled right. I try to write gramatically correct in all languages I know.
But I won't be mad and tell a person to use a dictionary if he tells me something good bus misspelled. So I agree with Emre on this point.

Sometimes I forget english completely when i see someone... and the last thing i think about is spell-check...