Different experience? They just snatched out the UMD drive and gave it some internal memory. Hardly a different experience especially considering that UMD hasn't been much of a success and there seems to be a relatively healthy segment of owners who use their memory sticks for their PSP content.
Sure it´s a different experience. Your games will load much faster, you can have 10-20 games loaded and always at hand (number depends on game size). You are also totally dependent on some kind of download service, which may appeal to some people others not at all.
The PSPGo is also considerably smaller which matters a lot in the portable space. Remember the price premium that small mobile phones used to carry before they became common?
Using myself as an example I never considered buying a first generation DS or PSP because I found them to bulky. The PSP3000 is still a fairly big device to put in your pocket. The PSPGo seems to be in the DS territory sizewise and will probably sell really well in Japan just because of that.