I use Acrobat 5 at home and (don't laugh) Distiller 3 at work. The boss is too cheap to upgrade beyond PM 6.5 and Distiller 3 - we don't even have a copy of the full Acrobat. Unbelievable for a small printshop, I know. But we don't make the film from layouts not created in-house (these are done at a service bureau), so anything received that would require anything more sophisticated than what we have is sent to the filmhouse. Anything I create in-house from PM that is to be printed B&W only we make our own film from clean laser copies of the printout. Otherwise either the original PM package is sent to the filmhouse using 'save for service provider' OR as a high-rez PDF generated using Distiller 3. Nothing wrong with this level PDF (V 1.2?) as - of course - it never causes any problems on the RIP. Only newest version PDFs seem to cause hiccups when RIPped on older RIPs.
We're still fairly backward with our other Adobe apps too - older versions of Photoshop and Illustrator - but again, they do the job required, so why spend the money upgrading? The only time I have ever wished I had a newer version of a software at work was in my previous job (also at a small printshop) where the layout application used was Coreldraw. They only did small jobs - lots of business cards and programs and brochure type stuff, so CD was OK. BUT considering that this business was based on CD, I couldn't believe how old the version we were using was. Can't remember the actual versioin number, but was the one before CD was able to import PDFs.
What do you use at work for your layouts?