Thanks for the nice comments guys, I really appreciate it. I enjoy doing these videos - I wish I had more time to devote to creating them. I have a list of about 40 or 50 that are on my to-do list!
I know you're slightly positioned to favor Tektronix equipment

but I was wondering if I could get your thoughts on the least expensive scope I could buy that would serve as a good digital signal station monitor.
W3AGT
Yeah, I'm a biased towards the Tek stuff. As for a station monitor, it really is quite hard to beat an analog scope. Most of the inexpensive digital scopes don't have the refresh rate to create a decent RF envelope display, and many will often alias the RF signal when using the lower horizontal time scales that are necessary for typical phone RF monitoring. Some will have display modes (such as peak detection) that will help, but you wind up with a very monochromatic envelope which doesn't have the same look, feel, and "value" that the old analog display has. I don't have access to any of the modern inexpensive DSOs, so I can't give you a first hand recommendation.
To get an idea of what a typical analog scope will give you for station monitoring, check out this quick video:
http://www.youtube.com/watch?v=2D83xp3H5BoI'm sorry if this doesn't directly answer your question, but unfortunately I don't have a way of evaluating the new/cheap DSOs in this application. My 10yr old TDS2000 does an OK job, but not nearly as nice as any of my old analog scopes when used as a station monitor.