A friend of mine absolutely hates Adobe Acrobat (and the PDF format.) He hates it with quite a passion, but I've not pressed him for details on why.
Acrobat does have some things that are understandable which may annoy people. Its fairly big (though if you have the reader, you can pull the plugins from that respective directory to make load times faster.) Its fairly expensive for the 3D or Pro versions (although you can get most of the functionality for printing PDFs using PrimoPDF.) Its a read-only format in general (although exportable to Word and other items in 7 and 8 with some fiddling with the output.)
Call me naive, but I can't figure out why the dislike for Acrobat. I use it all the time for archiving scanned documents (its nice having vital documents scanned as PDF/a files  for secure storage.) I also use it for saving Web confirmations of online orders, bills paid, or eBay auctions.
I also use it to send files as attachments to people who do not have (or don't care to install) PGP, and make sure the stuff I send them doesn't get changed in transit.
I'm not saying Acrobat is a tool for all jobs (if you want an editable document format, use OOo, Word, Excel, etc.) , but for a lot of things (pretty much if you do anything with the print/prepress industry, you WILL use this format) it does its job remarkably well.
I just can't figure out why someone would consider Acrobat so bad, that they will blow a gasket if anyone merely mentions it, much less has the "A" icon on the desktop.
: PDF/a is a subset of PDF intended for long-term archiving of documents. Acrobat 7 can make the files, Acrobat 8 can preflight/convert existing PDFs into PDF/a.