Hungary is similar to most European countries in terms of visa restrictions, traffic signs, electricity and other standards however there may be a few things you aren't aware of.
Language: Hungarian, though English and sometimes German are well understood in most restaurants and tourist related businesses.
Currency: Hungarian Forint (HUF)
Taxes & Refunds: 25% VAT (lowering to 20% in 2006). Tourists can claim back tax on purchases of more than 50,000 HUF and receipts can be stamped at the border and airport. More about Hungarian currency issues here.
Tipping: Generally add 10% as a tip to taxi drivers, restaurants etc. Also it's common to tip doctors and others that provide a service. Some restaurants add a "service charge" to the bill, in which case tipping is not necessary.
Visas: Most visitors from the EU, North America and Japan do not require a visa unless studying or working in Hungary. More about Hungarian visa requirements here.
Population of Budapest: 1.8 Million
Driving in Hungary: Driving is on the right-hand side of the road, and generally an International Drivers permit is required for foreigners. This can be obtained in your home country, usually by AAA for Americans, or CAA for Canadians.