It really depends on why you want to have your apartment appraised. If you wanted an estimate of it's value, have a look at the Trulia real estate guide for your zipcode. It will help you calculate your apartments market value, and it's free. If you need more help have a look at StreetEasy.com, Craigs list, or have a licensed real estate broker come by and take a look. If you wanted to be able to say to a prospective buyer, "my apartment appraised for $XXX,XXX and this is why my asking price is $XXX,XXX," then an appraisal is not a bad idea. Keep in mind though, that an appraisal may come in below the current market value.
Hope this helps. Good luck selling your apartment,