I love having the arrivals lounge. Here are my two experiences:
1) Flew with thirty people to London, but I took UA C, while they flew DL Y. With two hours to kill before they landed, I went to the arrivals lounge where I got to take a nice shower, have some breakfast, check my email, and just have a bit of time to relax. When I met up with they group, they looked a bit bad, while I was refreshed and ready to go ^
2) I went to Frankfurt in early March. Met up with another FTer around 12pm, but I landed in FRA at 5:35am

.. Visited the LH Welcome Lounge where I took a shower, caught up on the 85 FT emails I had received, and again, spent some time relaxing. Without the lounge, I would not have been in a such a good mood. I was able to check into the hotel at 10am, but I doubt they would have let me check-in at 6:30am!
I fully support arrivals lounge, especially after long TATL or TPAC segments.