Having stayed at the Holiday Inn on top of Roma Street Station I can say it's certainly conviniently located transport wise to get to and from the airport (it's the station that the Airport train starts from/terminates at). Certainly not as flash as the Sheraton, but it's clean and neat - all you'd expect from a Holiday Inn
. There's not so much life down that part of town though, you'll find more dining options around the Sheraton. But another option to keep in mind anyway.