I just recently decided to JB my ATV 2. It is updated to to 5.3 and I have not saved previous blobs. As I understand it my only option at this time is a tethered JB. As I don’t have access to a laptop that is not the best option for me right now, however, if I go ahead and JB it, does it function normally if not tether booted? Should I just wait to see if an untethered boot is released for 5.3?
Once you have done a tethered jailbreak then the ATV can no longer startup after a power off (or ahrd reset) without going through the tethered boot process.
I think it is unlikely that an untethered jailbreak will now appear for 5.3 (although you can always hope) as the jailbreaking community is now likely to be looking at iOS7 based firmware (such as the 5.4 for ATV). It not expected to be more than a month or two now before iOS7 goes on general release so this is likely to be deemed more urgent - and it is relevant to iPhone/iPod/iPad devices as well as ATV.