I've seen this a lot too, people commenting about it, and my anecdotal evidence of it too. ANd so often you see, "oh, it must be your router" explanation. Well, I have a PS3 and one of my close friends has one (comparatively, most of my friends have 360s, it's just the console we all usually play on), and since forever, the PS3 has downloaded far slower than my 360, and my friend corroborates. ~100 MB updates to games take 5 - 7 minutes to download, which is ridiculous.
For some info, I have a 100Megabit downstream, one of the fastest consumer-level downstreams in the US. I regularly download on the 360, my laptops, computers, mobile devices, and so on, at normal, high speeds. The PS3 slow download is with both WiFi and wired, and it's a major pain in the ass... and it's been at three separate residences, with two different ISPs (Verizon and now Charter), and with a number of different NATs.
My house, currently, has a pretty complex NAT system... Modem brings the internet into the house, splits off into an 8-port wireless N, which then diverts one cable down into my basement into a business-grade 24-port switch, which I then run 5 wires from that up to the bedrooms & office on my first floor. From there, each bedroom has 4 port switches that divide up between devices. With 100Mb coming in, usually each room gets about ~25Mb to split up amongst 4 devices. Generally, it's very rare to ever hit 25Mb on any device because the service you're using (XBL, or some consumer-grade FTP, hosting services, etc) is rarely going to dish 25Mb to you. But, still, on my PC I usually get about 4 - 6 mega bytes per second on high quality connections, X-Box live I can't measure it, but I download 2GB files quickly, within 5 - 10 minutes.
So, maybe it is my router settings, but even if it is, I come back to blaming the PS3 or PSN for this, because why the hell should every other device (including a personal home server, numerous multi-OS computers, mobile devices, game consoles, printers, etc) work pretty much flawlessly and at high speeds, and then my state-of-the-art PS3 runs at a ridiculous fraction of the speed of everything else?
rant over, srry.
(edit: I have an old 60gb PS3, fat boy)