I have a tv that the tuner circuit died in. so I got a set top box from dick smith for $30au.
now dick smith has shut down its highly unlikely to get another but you can find features ranging from on screen tv guide, USB recording, major advances in the home theatre sound etc..
the issue is what do you want?
the more expensive ones let you incorporate Netflix, presto, stan, Foxtel etc (internet movies and shows on demand) catch up tv if you have it (watch programs that have aired on free to watch) as well as act as a media hub so you can run around the house on a tablet streaming the programs while watching another on the tv and recording a 3rd or 4th even.
as I said there are a myriad of devices out there... if all you want is to convert digital stream to analog then go cheap, they last well mine has.
if you want to move up and try something new shop the heck out of the item before buying it, DON'T listen to sales people, get online and ask in forums what each item means, a sales person is there for 1 reason, TO MAKE A SALE, we here on the forums are here because we want to educate and learn. no profit for us except seeing the hobbies we love expand and grow