The former Scotland Under-21 star is now skipper of the Spireites and is wanted by a host of other clubs.
He said: "It has been great so far. I was even offered an extension to my deal in December but I want to keep my options open and the gaffer Lee Richardson knows I want to play in a higher league.
"I definitely made the right decision coming here.
"The fact Brighton offered £100,000 for me in January confirms that, while other clubs like Luton and Oldham have also been sniffing around.
"Chesterfield rejected the Brighton bid as they wanted more so I must be doing OK.
"The biggest thing for me has been playing in my preferred position in central midfield.
"But I also wanted a change when I left Killie. I was fed-up playing teams four times a season.
"Last Saturday we played at Bradford in front of 14,000 fans and that's in League Two. That's the attraction of down here and I'm thoroughly enjoying it."