My Sony Reader can also render a PDF acceptably--if I use the teenie-weenie font size.
But I find it very difficult to read that small size.
And they look like trash when I select a larger font size.
Do PDF files flow and remain readable on the Kindle when you select a larger font size?
I'm not able to modify the font size of the pdf files in Kindle
(I'm new to Kindle, so there might be some option that I don't know).
So, unfortunately no reflow (like Adobe Acrobat Reader for WM, for instance),
or at least, not for now.
I can only select an area (not a text, just like when you select an area of an image to crop, for example)
and increase its size and that, of course, is no an option for me.
The text is perfectly readable after the conversion to azw (the Amazon Kindle format),
but you loose some formatting: some programming code, for example,
might be not easy to read (long SQL statements and result sets, for instance).
Some images (like diagrams) could also the difficult to read,
but the plain text is perfectly readable after the conversion
and no further modification is needed.
Do not own a kindle nor do I ever intend to buy one.
Is it specifically the Kindle that you object to? Because it's proprietary? Because of Amazon's control? Privacy?
Or do you object to ereaders (Sony Reader, Nook, etc.) in general?
No. I have nothing against the Kindle. I read ebooks on my computer. Personally, I do not see the need for an ebook of any brand. I would rather get a smart phone that lets me read ebooks. That way I have a device that serves more than one purpose.
My wife wanted one so we got one. Personally I'm not entirely happy with the lack of control that comes with the platform - being able to read ePub content would have been nice, for instance, likewise being able to read arbitrary HTML or PDF content loaded via card slot or LAN (you can load PDFs on the current Kindle, but you have to send them via email... it's pretty convenient, but I do tend to favor a more direct approach)
In particular, personally, I wouldn't be satisfied with being unable to load a bunch of stuff from Project Gutenberg. (They have HTML-formatted stuff these days, right?) Converting to PDF is far from ideal because it forces formatting choices - I haven't looked through the Amazon store enough to know how many public domain titles are available for free, as they (mostly*) should be.
(* "mostly" because there is value in a good edition, especially an illustrated or carefully formatted edition...)
I can plug my kindle into a Window computer and it mounts the kindle like it is a USD thumb drive. Then I copied my pdf file to the kindle, "ejected" it and my pdf's were there. Ironically, I not know how to email a pdf to my kindle. I'm a bit taken aback to learn that such a thing is possible. I hope my kindle does not start getting spam pdf's. 
I don't know if this is a new Kindle/old Kindle thing but my understanding was that email was the only way... Don't know, really.
As for email - you have to whitelist sender addresses, so at the very least someone hoping to spam you would need to get the sender address right. This was actually a challenge for us the first time around, we didn't know you had to whitelist the sender address, so our attempts to send docs over just failed.
You can see what it is at:
Home -> Menu -> Settings -> (page 2) -> Device Email
You can change the address online, and set up allowed source email addresses. I don't remember what the default settings were.
Also note that if you send a document to be converted, you might get charged for it. There's a free email address, but it doesn't get sent directly to your device.
I do that with my Sony Reader. But I don't have a Windows PC. I added a line to my /etc/fstab:
UUID=0000-XXXX /mnt/sony vfat defaults,users,noauto,rw 0 0
Then I use the commands
mount /mnt/sony
and
umount /mnt/sony
I think I got the UUID from the lsusb command.
No. I didn't made efforts to get a kindle.
No. I love the smell of books, and also love to own books and share them 
My wife got one some time ago to be able to read her fan fiction offline as it would be very awkward to print it all out and she is totally amazed with it. I was also very impressed when I saw the quality of it. It simply looks like a printed page and the tool itself is very flat, lightweight and robust enough for daily use.
I can't read on the computer for to long, so I have a hard time seeing myself being able to read on any e-book reader, for any real length of time. Maybe cause it's not nearly as bright it might not be so bad, have to give it a test run.
Nearly 18 months after posting this poll, I finally got a Kindle Touch today. I paid nearly 65% more for it in Thailand (because of taxes, duties, etc) than it costs on the the Amazon web site; but as painful as that sounds, it was worth it.
What a great device! Amazing!
... and much better than using my Android Galaxy Tab with a Kindle app! Much easier on the eyes and so light weight.
A month after buying my first Kindle. I kindly recommend getting one. I'm catching up on a lot of science fiction these days, reading lots of scuba diving books, and some classic literature every now and then.
Now, it seems natural to have a Kindle book reader. The Kindle is not the most technically advanced device I own; but it is great for what it does, downloading, storing and reading books.
Yup.
A Kindle Keyboard for about a year.
The biggest problem, or annoyance, I've experienced with my Kindle is that many illustrations do not translate / format to Kindle format very well. I"m reading a Kindle book on fiance at the moment and the tables, charts, and other illustrations are nearly impossible to read.
sometimes I've problem with Perl codes in books.
But with Amazon new format (K8 or awz3) which is a non standard epub3 the situation is getting better
I had problems with scientific equations and formulas in most Kindle books I've read as well.