Western-compatible ATMs are now standard especially in Moscow/St Pete. Be certain to tell your bank you are going, some are so suspicious of transactions suddenly starting to come through from Russia, having had so many bad experiences, they will put a hold on your card and call you at home - which is no good when you are in Russia. Use the ATMs which are inside the bank office - they have good logic and if you insert a western card the questons come up in English.
Credit Card acceptance is still less common.
In comparison to the substantial overnight train service, the daytime high-speed services, at 200 kmh/125 mph are less popular, only one or two a day. They do take about 5-6 hours and like amost all Russian trains are punctual to the minute. The rail cars look little different to standard Russian ones outside but have new seats inside, and are pulled at speed by the standard Czech-built Skoda locomotives which the Russian railway has thousands of. Most daytime passengers seem to be overseas visitors, I guess it's just a Russian tradition to do the trip overnight.