I am a long user of HP calculator, in fact since 1991 and I have still kept my HP48GX with my license of MetaKernel 3.0 (paid 120 FF or 18€). I like the RPN way of doing thing, and I was lightning fast doing math thinking in my head like a RISC processor would do, small steps with limited operations, and a lot of intermediary results. I bought four calculator in the past 2 months: a HP48Gx , two HP 10 Business and a 20S scientific for a total of 5 euros!!! tripling my collection size. My section concerning the HP calculator is outdated but still online.
Don’t forget also to visit hpcalc.org (http://www.hpcalc.org), the premier source of software for and information about the HP 50, HP 49, HP 48, and HP 28 RPN programmable graphic calculators and the HP 38G, HP 39, and HP 40 programmable graphic calculators.