Does Google see this as any old 301 redirect, or is it a bit more lenient, as the rest of the URL will be staying the same?
Not sure exactly what you mean by this.
Not knowing your expertise level, I need to point out that if you actually set up the redirect on your server, in your case using ISAPI rewrite, Google will see it as such. If you just remove the .asp extensions and expect that Google will figure out that this is a redirect, you're in for a nasty surprise.
If you're asking whether this kind of change will be less traumatic and easier for Google to figure out than a domain change, the answer is yes. Ditto, Google will probably figure this out more easily than if you made nav structure changes.
Note that you will have to change the internal nav urls in your page code as well as do the rewrites. Not sure how your pages are generated... but if you can change your page code urls to absolute urls, you will minimize chances for mixup.
Let me add, just as with any change in URL structure, there most likely WILL be a bump in the road for traffic.
As I understand your question, you are asking if this particular change might go smoother than a complete URL renaming. Theoretically, I don't see why anything like that would be written into the Google algo, but I have no actual data.
A technically sound rewriting of all URLs isn't all that traumatic these days - especially if you can get some strong external backlinks to change over and also attract some new ones. But all the technical aspects need to be nailed down 100%, or else it can get really nasty.
i have not experienced google treating some 301 redirects differently from others. if this is just for cosmetic reasons i would not do it. i have handled many redirects and #1 its a pain to setup and make sure nothing gets overlooked #2 there is some slight link evaporation from my experience.
when in doubt keep it as simple as possible for the search engines.
jimiedge, I am sorry as I didn't notice that you are a new user. Welcome to the forums.
I guess that you had the question because you felt that it is only a simple change towards the end of the url while the rest of the structure is retained as it is. But note that even a one character change in the url makes it different from the original one and a redirection is necessary for google or any search engine to locate the new location.
Thanks, and sorry for the terrible parlance of my question. I think the tedster fella got it the best - I was just wondering if anyone had noticed that removing a filename extension was less traumatic to a site than changing the whole URL.
My thought was that it wasn't, and I'll find out in more detail soon.