Heh, I wondered the same thing. And I eventually just bought the router (except I bought the Linksys 802.11g with Speedbooster, I've always been partial to Linksys). Thing is, I upgraded from an 802.11b, at 11mpbs, so I can't compare the speedbooster to just a normal 802.11g.
With the Intel 2200 in my i8600, I tested the wireless speeds using www.nyc.speakeasy.net
(I've just always used this site). It came out at about 3200 download speed, 250 upload. This was a tremendous increase from using 802.11b, which was under 1500 I believe.
Well, of course I was wondering how fast it could get if I bought the pcmia speedbooster card. Went out to bestbuy, decided to get it, test the speed using speakeasy, and if the speed wasn't significant, just return it the next day at bestbuy.
Well, I kept it :-D Wireless speed is faster or just as fast at wired. speakeasy reports 4000-4100 download speeds now, desktops report 3900-4000 (depends on time of day).
Without the card, just going with the Intel 2200 and the router, everything was fine though. Wireless gaming was no problem, ping levels were fine in rooms, everything was great. No complaints there.
But after buying the pc card, it's just better. Probably unneeded, but still, It's kind of neat to have wireless moving at these speeds. I like it, and I still don't consider it by any means a waste of money (even though my friends think it was).
So in a nutshell: Intel 2200 and the router is awesome (dont know how much better it is than just normal 802.11G though), and things reach desktop speeds with the laptop card.
Up to you if you need it to go that fast.