I switched to HydroCAD for site hydrology applications after discovering it on the eng-tips forums, and am a big fan. Peter is a very responsive guy when it comes to technical questions, and the license is very affordable. Your modeling challenges down on the Panhandle are different than up here in Atlanta, though. I've done half a dozen panhandle projects, half a dozen SWFMD projects, and two or three in other WMDs in Florida so I have a good sense of what you're up against.
I know Peter will say HydroCAD does variable tailwater and interconnected ponds, and it sorta does, but the models have a tendency to explode once you connect them up in that way. Then you have to spend time adjusting time increments and calculation methods and those sorts of parameters in HydroCAD to get any output that's meaningful. So while I would consider it capable, it's touchy. XP-SWMM is much more robust at that particular task, from a modeling perspective, despite the headaches it has producing deliverables for a report. It might be nice (looking at you Peter) if HydroCAD had a button that would re-run a model over and over with different "finer routing" settings until it found a setting that didn't oscillate. One thing I really liked about XP-SWMM is at the very end of the output file, it would tell you what your continuity error was, so you could see if model fluctuations were causing an additive error that either removed or added water into your routing analysis. I wish all software had that. XP-SWMM was definitely very powerful.
I've never used it, but supposedly ICPR is the bees knees in central and southern Florida, for site development work. I've even seen guys up here in Atlanta using that, although most of our site stuff doesn't need variable tailwater analysis. I get the sense that anyone using that up here is a FL transplant. I've often thought that if I had to get back in to XP-SWMM style modeling, I'd just learn EPA-SWMM, since it's free. I've only used it once, to tweak a flood model put together by another firm. I was able to do what I wanted to do in it, but I don't know how much of a headache it would be to model something from scratch.
For flood modeling, HEC-RAS is still the thing to use, and probably always will be.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -