I've got Altiverb and use it occasionally, by no means is it even in the same league as any of the high end hardware units. You are right for now. But, in the near future PCs will so outpower dedicated boxes it will be scary.
I've been hearing this since the 80's. The more powerful PCs get the more bloated their OSs and apps get. Parallel computing is where the REAL power is and using hardware outboard frees up my puter to do other things, just like the PC that I run my soft synths on etc. If you think about the chips in a 480 and their age, they probably are NOT more powerful than what you get in a mac 1.5Ghz
It's not about the power of the individual chips, it's the entire amount of computing power that's available to the process and how the algorithms are designed to take advantage of it. The more complex the algorithms, the more dedicated computing power required. I think we can all agree on that point.
If you could dedicate an entire computer to just doing reverb a 1.5g mac would probably do a great job if it were programmed with some great algorithms specific to that machine, but...oh yeah, that's what outboard is!
And D, if you look at the top of my previous post you'll find an apology for being unduly harsh. Glad your life is full, but we could all use some more good luck