The advance check in was terminated for many airlines for 2 main reasons - cutting the cost of the staff in the separate terminal and lack of demand at most times. At first it was offered for free, then they charged 20 NIS (like $4.5) for the service. It is still available for El-Al and some airlines. I might be around there later in the week and can check if Swiss is on the list.

In TLV, you should arrive about 2-3 hours before the flight. If you have a host in Israel or some Israeli that knows you, it might be better to bring him/her along as it might cut some time from the security questions.

Once checked-in, there is nothing much to do in the check-in hall. Most of the shops and views are from the 2nd floor, past Passport control and security.

There is no observation deck. The terminal is one long building that streches east-west with the north wall being all glass. The planes are parked and not connected to the terminal by gates. Most plane parking spaces are to the east and west of the terminal and are not visible from it. What you can see is the end of the arrivals runway (very near) and most of the departure runway (quite a distance to the north). Photography is allowed but you won't be able to catch much from the terminal.

Around mid-2004 the new state-of-the-art terminal 3 will open and all this will change as this terminal will feature jetway gates, observation wall and mall in the check-in building, direct train service to Tel Aviv and more.