I just finished a couple of stays at the LM Barcelona. A couple more pieces of info that might be helpful, especially for those who are especially cheap:

Through the end of the month, the Renfe C10 express train between BCN Aeroport and Passeig de Gracia is free. The train takes ~25 minutes, and it's about a 10 minute walk south to the LM from the Passeig de Gracia station. For those who want to spend the big bucks, it's another .65 euro (if you buy a T-10 metro card) to take the subway down to Catalunya metro station. Ask at the airport train station, and they'll give you two train tickets--1 for the outbound and one for the return.

When the train ceases to be free in February, the airport is still within zone 1, so you can use a T10 metro card (.65 per ride) for your train ride from BCN to Pasieg de Gracia and take metro to Catalunya (transfer is free) or switch to a different eastbound Renfe train at Barcelona Sants station (transfer is also free) and go one stop to Catalunya.

Also for those who wish to avoid the 25 Euro hotel breakfast, several stalls at the Mercado de San Jose (about 1 block south of the LM) have very good fresh-squeezed juice blends for 1 Euro each (.50 each after 6pm). The fridge in the minibar has a shelf if you want to buy your juice the night before and keep it in the room.

Re: SPG benefits, as a gold, I didn't get an upgrade on either of the two stays (one was Tue-Fri, the other was Mon). I did get the bottle of mineral water in my room, however.