Not really for PC P&C, they only have excellent warranty service, despite the fact that Seasonic has made about 3 lines for them.
You're just being a fanboy now.
Most of the other companies I brought up also have very good warranties and some also have CSRs on the major hardware forums, especially OCZ and Corsair. That isn't a good reason to pay more for anything.
PCP&C used to have some great deals a while ago, but the prices on all their units seem to have increased recently. Their 610W model is still a good buy but the others are a little too expensive now compared to similar models. And most of the Seasonics are slight ripoffs because you can get the same things cheaper as Corsair and PCP&C rebadges if you look around a bit.
Other than that, it's just too spotty for some manufacturers--a bunch of good units and a few bad ones--and they see "deal deal deal!" on the bad units and may grab one instead of the slightly-more-expensive but much better good unit.
I don't think any of the brands I mentioned have any current models that can be described as "spotty." The Seasonic-built units are excellent but are by no means "much better" than the others. If you need the absolute best voltage regulation anyway, you should go with a Zippy server unit, not a Seasonic.
Good luck finding Zippy in the USA. I've been looking for a while--I can't find Zippy, I can't find Emacs. And for PC P&C, definitely only a few are even within "range" of the normal person. I swear by Seasonic--my uncle by PC P&C. Other than that, yeah most have decent warranties. But still, if you're telling someone to buy say Corsair, I'd always say Seasonic-built, as CWT-built are not as good quality. Even so, CWT does have some good-wattage units at good prices as well, but not all of the are best.
Besides--I generally look at other Seasonic-built units while looking at Seasonic-branded units... meaning I take a look through Antec and Corsair at the same time, as odds are they'll have the same or slightly better a deal. Other than that, I've not been able to beat Seasonic's OEM (SS-___ES) units often, other than the fact that they have two SATA connectors. Even so, building a new system with that 500ES, odds are you'll also get some molex-to-SATA dongles that'll work just fine.
I am quite a bit biased, though the positive side of it is I'm biased towards good build power supplies and against those that aren't quite as good, while still being about the same price.
That and NewEgg has a horrible time with all... 567 normal units plus 53 more server-specific units. I can't just set people loose and say look for this, and I even get overwhelmed--I can't research each and every unit to find out who made it, though often I can take a look at compare UL# of similar units.
I guess I generalize too much--I help out at another forum where there are countless other people who simply don't know what they're doing. Last correction I made was a Win Power 750W for like 30-35 GBP, switched out for a Corsair VX450 for about 38 GBP. It's not like the person's system would need it all--while Pentium D's are hot and hungry, they're not drawing 300W on their own. HD4850 runs about 120W max, plus say 95W for graphics, 10W/drive (40W), and a bunch of USB stuff, and you still are running comfortably. Stuff like that, I just look at Corsair, Seasonic, PC P&C, and that's about it.