life changing when I started using that for multitrack recordings..
Ardour works fine with an Audio Technica AT2100 USB (I tried it and can verify that it uses the standard USB host drivers without complaint) for both I/O and works out-of-the-box with most of my audio interfaces and an XLR mic.
My 2¢: Based on my experience with podcasters, I wouldn't recommend a Snowball for beginners doing spoken-word recordings. This is a "worse is better" scenario where a cheap dynamic will give you better out-of-the-box results than a condenser mic like the Snowball, in part because it forces speakers to get closer to the mic (increasing the ratio of signal to ambient noise), and in part because dynamics usually can't record anything over ~15 kHz (spoken word tops out around 8 kHz).
A Snowball is fine for folks savvy enough to use an EQ to roll off everything over, say, 10 kHz during production.
I alternate between an sE V7 dynamic, a Blue Encore 200 "active dynamic", and an AT2035 at my desk for recordings. The Blue is something I'm just testing but the other two microphones are great for different things. (Anyone who hasn't checked out a sE V7 should; for my money it's the best thing in the "SM58 range" of dynamics, with a really clear sound for a dynamic. And the damned thing won't roll off your desk if you have it handheld...)
You get around this be setting JACK to use the snowball device for capture only (and by doing so you are using its clock) and then attach whatever device you are using for monitoring as a JACK client using zita_j2a from the zita-ajbridge tools package.
I do know that programs like Adobe Audition on Windows offer that in a plug-and-play way.
if price is a problem there are several other environments on Linux for composing and producing. even something as simple as lmms can be made very powerful. you can also build drum patterns with hydrogen. you can use stuff like openmuse to score music, you can download some decent soundfonts (fatboy is good, timbres of heaven is amazing) to get more juice out of your midi, etc. then if you're into generative music there's stuff like supercollider and puredata, or dsl's like sonic pi for ruby and overtone for clojure that can drive the supercollider synth. or there's even languages like chuck, all sorts of interesting possibilities for audio.
anyway i guess my thesis point is there is always a way to get it done, as long as you keep at it (which it seems like you indeed have been doing so ^5)
But it's not an Ardour replacement. Some of their features overlap, but you can't do things like record long clips of audio in Renoise, while that's a core feature in Ardour.
Also, the workflow for Renoise is just not something most people are used to or will want to spend the time adjusting to -- though I certainly encourage them to give it a chance, as it's great alternative to the mouse-oriented piano roll workflow in traditional DAWs.
So I think for most Linux users, Ardour is going to probably be the DAW that they're most used to and the one most appropriate for recording and manipulating audio for screencasts and videos, with Renoise unfortunately relegated just to music production by tracker fans.