More than you wanted to know? I got ya covered.
I bought a Pro IV about a year and a half ago. Versatile? That's not the word I would use. When folks ask I usually say, "Beast." Thunderbirds in general, are big basses but the neck is narrow like a J bass. The reverse body style feels... different. I classify it with the big bottom girls like a Stingray or a Tele Bass. But even there it really is its own thing. If you haven't played a TBird before, I would go find an incarnation to feel it.
The Epi Pro IV in particular. They dropped the street price on the Pro by $100 recently so that's pretty nice to start with.
-The neck-thru design with the humbuckers sounds great. Mine isn't boomy or emaciated, it has a solid sound. I've got some Ernie Ball Cobalts on it right now and I like them on this instrument.
- Design. The head stock on kind of an issue. The head is long so it doesn't fit in a standard case or gig bag. Expect another $90 for a case to fit it. The D and G strings like to sing between the nut and tuning post. There's enough down force so they don't rattle in the nut, but they're long enough to pick up sympathetic vibrations. I ended up putting a vibration dampener meant for a tennis racket between the D and G to make it stop.
- Finish. Mine has a natural oil finish and it is gorgeous. But the oil from the factory didn't hold up for long. In the end I refinished the whole thing with gun stock oil and wax. Now it feels nice and looks even better. If you have the time and ability I think it's worth it, but if that's not your thing I would steer away from the natural oil finish.
- Mine came with the strap nut in the corrected place, where the neck plate would be. It's very comfortable with a 3-inch strap and doesn't neck dive on me. However, I have a lot of control over the instrument's attitude with my right forearm on the upper wing so that certainly helps.
- Hardware. The bridge is tight and solid, I've never had a problem with it. The tuners are smooth; the knobs on the pots turn smoothly and quietly. Sometimes I get a bit of hiss from the electronics but an EQ pedal clips them our easily. I'll probably shield it one of these days. I can't believe I didn't notice this before tonight, but the fret ends on this thing are spot on.
But you asked about versatility. I keep mine because it's the best sounding pick style bass I have. I like the finger style sound but the neck is too narrow for my bears paws to play comfortably for longer periods. The slap sound is okay, but it's no Jazz. Travis picking is alright but nothing special.
I think if you're looking for a versatile instrument in that price neighborhood I would suggest trying a Sterling (SBMM) Ray34. Still a humbucker and active EQ but it slaps a lot better, Travis picks better, and for my hands finger styles better. I found my Ray34 at a guitar barn as last years floor model for $500 with a good gig bag.
Is the Pro IV good bang for the buck, at $400 I think so. It's an intermediate instrument, one you get it dialed in it's pretty nice. If it were a $1k+ instrument I'd be miffed about how much work I've put into it. If it were priced sub-$300 I'd be super stoked about what you could get with some time and know-how. But if all my basses went up in smoke tomorrow, it would not be the first one I replace.
One last word, I'm not so sure about resale value on these. I know there's the Thunderbird club here on TB, but they're not super popular to begin with (the basses, not the people). On top of that an Epiphone still says Epiphone on the head stock even if the greatest luthier on the planet sacrifices a goth to the Plek gods to make it a perfect bass.
Hope that helps.
TL;DR - Yeah it's alright. I prefer a Ray34.