Got a TTP last year. Back then they closed all the airport landside registration locations except for Haneda, the alternatives being airside or the regional immigration bureaus. I decided to do the latter in case I am missing anything and I have to go somewhere first. Also came prepared by buying the revenue stamps off Japan Post first. The Osaka bureau was surprisingly convenient. No queues and they even sell revenue stamps at the ground floor if you didn't come prepared. Done in 30 mins. The female staff did not speak any English, though my very sparse Japanese was sufficient to get the general idea (TTP valid up to 3 years, must keep visa waiver registration valid to continue using TTP, but can keep using the same card until it expires).
Benefits I noticed include the ability to use the card as ID to check-in to hotels. Never had to whip out my passport during my last trip when checking in to hotels. Additionally, holding a passport that got less than 90 days visa-free to Japan, I was pleasantly surprised to see the stay period printed on my card is 90 days. Not sure if this is just a bug, I really want to ask MOJ whether this is intentional.
Unfortunately, the tourist-only benefits once you arrive e.g. tax-free end up being considerably slower, as you don't have the standard "landing permission" QR sticker, and immigration refused to provide it (I asked after passing through the gates). With tax refunds, I had to tell them when they flick through my foreign passport that there's no current entry sticker and try to get them to look at my card. Some diligently flick through the passport regardless. Most shops end up accepting it, though there are shops like Don Quijote that wouldn't take it at all. Flashing the card at JR stations took 20 mins for the ticket person to get the station master to study it and confirm my Temporary Visitor status prior to issuing my regional rail passes.
Arrived in KIX midday during what's supposed to be sakura season (weather changes massively delayed it), normal queues were quite long but not crazy (about 25 mins). TTP meant I was through in 2-3 mins and the priority tags meant I was mostly waiting for the remainder of my traveling party.