Mark, I've made some comments about the Kindle browser on my blog (http://www.codingscience.blogspot.com/) I have successfully used it to access my work e-mail (Outlook Web Access) whilst on my travels. It is a bit like going back to Black and White TV (God that ages me!) but still quite usable (but roll on colour e-paper). My biggest problem is viewing scientific papers (usually only avail as PDFs) in 3 columns which is e-reader unfriendly. If anybody knows of a tool to reformat these to single column reliably, 'I'll be over the moon' as it is a bit of a deal-breaker for some of my colleagues. I say reliable - I tried tools like calibre and stanza (and a google code project whose name escapes me - I said I'm getting old) and get weird effects (Which I'm beginning to believe is down to quirks of PDF format when having multiple columns with diagrams and images (:-() rather than the programs).
Anyway, back to original question - Browser is usable but I wouldn't use it as the 'weapon of choice'. Or put it another way don't try and use a hammer to put in a screw... :-)
Hope that this helps, Mark