In my opinion, not anymore.
I bought Pokémon Dream Radar when I bought White 2, and it was almost worth the money. I had access to four Pokémon I really wanted: HA Slowbro, HA Swablu, HA Riolu, and Landorus-T. I spent a long time on that, catching more Cloud Nine Swablu than I can care to count, and then I saw Tornadus-T. Naturally, I got really excited. I caught him second try, and when I transferred him to my game I saw his nature. Rash. Rash. It dawned on me that there was no soft-resetting, and I gave up.
Tragic backstory aside, Dream Radar was worth getting in the BW/BW2 era. After that, though, it just becomes outdated. The process of putting in enough time to catch all three Therians (Landorus is rediculous) is outweighed by how (relatively) easy it is to obtain them in Gen VI. If you can manage to nab one from the GTS, just keep trading it for another identical Pokémon (e.g. Thundurus for Thundurus). That's how I got both of my Timid Latios and Latias.
In short, Pokémon Dream Radar was worth it when it came out, but in my opinion – and others, I'm sure – it is not worth the time and effort reqired, as obtaining the Dream Radar HA Pokémon is much easier now in XY/ORAS than it was in BW/BW2.