I have 2 modern-maker basses. One from your list (Threlkeld) and another, IMHO, worth some consideration.
The Threlkeld is not one of Chris's typical instruments. The body is quite small (the ribs are probably around 5" deep on the upper bout and maybe 6" on the lower. The bass plays like a dream. Very low string hight, easy response, easy to get around, etc.
It has a deeper,darker sound but not really the "boom" that you'd expect in a larger orchestral bass. All things considered, it can still produce a good amount of volume.
The workmanship is great. Chris likes to give his instruments unique looks. For example, mine has a lot of blood wood accents and some brass inlays on the body. Also, this bass has been in the dry Colorado climate for the past 2 1/2 years and I haven't had any issues with cracks or seam openings.
I'm going to make some general pros and cons for the 5 or so instruments of his that I've seen and played.
Pro:
good workmanship
cool designs
sound quality: (especially on his larger-size models) they tend to have a big, cushiony sound. The sound is very pleasant to hear.
great setup: the ones I've tried have generally all responded quite easily
price: I think he may have raised his prices but still, I think you get quite a bang (boom) for your buck.
Cons:
sound quality: (this can be a pro or con depending on what you're looking for in a sound) I haven't heard any of his recent basses but, in general, the ones I've heard don't tend to have the most complex sound
finish: the finish is debatable. Mine has a satin finish and has held up amazingly well and I think it looks beautiful however, there are other new instruments out their that I like more.
The other new maker I'd suggest checking out is Christopher Savino. He works at Robertons in NM (violin turned bass maker). He's only made 2 so far and is currently building #3 (I have #1) which, I think may be ready for the ISB convention. The model he makes is based on a Cavalini that is owned by the Curtis Institute (maybe you're familiar with it).
Pros:
good workmanship
Looks: very attractive design. The finish is beautiful.
Sound quality: This bass has the ability to create quite a bit of sound (both arco and pizz). I wouldn't describe it as a bright or dark sound. It kind of has the qualities of both. In any event, to my ears, it has a very beautiful singing quality to it but also quite a bit of boom. Also, the pitches are very clear and will ring for days.
Setup: the setup is good, nothing really to complain about (but I think the Threlkeld may be better)
Cons:
Price: it's in the same price range as a Laborie. IMVHO, the price of new instruments is going through the roof. I don't think they should cost anywhere near what they do. That being said, I still bought it...
Finish: The finish, while beautiful, tends to chip rather easily. I've had to take extreme care to keep it from getting damaged.
Response: The response, while good and getting better, has been a little on the tight side. Part of it may be it needing break in or my needing to learn how it needs to be played. Either way, it's becoming easier and easier.
*edit*
If forgot to mention that while I do often use the smaller Threlkeld at work, this model would probably be considered more of a solo or travel type of instrument.