I believe you could always use the other ROKU features without Netflix, such as Amazon and MLB.TV, and now the other channels too.
But without Netflix, you are really limiting your viewing options. At $8.99 a month ($10.99 with blu-ray), Netflix is a bargain given the amount of online content you can get for it, not to mention the DVDs in the mail is an added bonus.
If you do not plan on having Netflix, I would probably wait until ROKU has official support for its built in USB drive (on the HD|XR), network streaming support from your home network, and Hulu or a few other content providers.
This way you will have a few more things to watch without having to either pay per movie/episode (like via Amazon) or be stuck watching podcasts only.
On the other hand if you just can't wait to try it, go for it but get the HD XR version since it has the USB port (which no doubt means that plugging external storage devices is definitely coming).