Such a utility word. It can mean your are thinking, imply you are concerned, just buy you time, fit in anywhere you don't know what to say. It all depends on how you use it and how the listener perceives it. Perhaps the most commonly utilised expression!
Today, language is filled with a multitude of such phrases. It makes the language a lot more flexible at the same time leaving something open to the creativity of the reader or listener.
The F-word, for instance, is the only word that can fit in as a noun, verb, adjective, exclamation and adverb. It has all possible forms possible in English grammar. Its potential has been exploited (and abused) to the core. The only problem being it is still a far cry from the needs of formal communication.
One such accepted word is "okay". Again used in a lot of places to imply a lot of things. Personally, an okay used anywhere but to suggest a tone of affirmation gives the vibes of disinterest.
But imagine..Wouldn't it be great if we had more of these words incorporated in our formal vocabulary.
Then, of course there are words which are a part of an individuals 'frequently used list' just like 'sheesh' is for me. I have been using it even for non-exclamatory remarks these days. Friends have accused me of being a 'sheesh'er.
Some of my favourite utility words from what my pals use are chop, badiya hai, sahi, awwwwww (thou this one has restricted applications), balls and pucao. (Will keep updating this list)
The only reason for concern is that we are losing touch with English Grammar as time passes. Not that big an issue thou. The purpose of language is communication and as far as that is served, kisko padhi hai!