Yes, streaming media over wireless real-time isn't generally a great idea because of connection drop outs.
However, Netflix clients actually buffer data before playing, and it dynamically re-adjusts the stream quality to ensure that there's always a buffer (aka never really playing media real-time). Because it uses a buffer, you are pretty much free to use wireless. The worse thing that will happen is that Netflix streams a lower quality picture to you if your wireless connection is really bad. Keep in mind that most people's broadband connections are 6MB/s tops, so your wireless network connection would have to be pretty bad to not be able to keep up with that.
If you have other devices that are truly real-time dependent around your media or want to future proof it, run a CAT5 cable for sure. If you want a cheap/quick work-around to get your Netflix stream to your living room, you can use wireless without fear of getting annoying video/audio breaks outside of a possible stream re-adjustment.
FYI, I have a 3MB download limit on my DSL line, and since my wireless access point is close by (the room next to my living room), I'm re-using an old Linksys Wireless-B Bridge (WET11) which only supports about 11MB/s. The Netflix client shows that it gets two bars short of max quality, and I never have issues with video/audio breaks. Unless someone starts using my Internet connection to download files while I'm already in the middle of watching a movie, I never have see the stream re-adjustment screen either.
I've also unplugged/disconnected my wireless bridge in the middle of a playback for short periods without getting any breaks in the stream either. Point being, if you want to save money, you have plenty of options to explore.