I'm one of those diehards who keep using CRT monitors in 2012 and I found that, in some cases and maybe with some effort, smooth scrolling is achievable with these monitors, even in 50Hz.
My monitor is a Samsung SyncMaster 753DF.
Here is my 704x576@50Hz
Timings copied from PowerStrip:
PowerStrip timing parameters:
Generic timing details for 704x576:
HFP=56 HSW=72 HBP=48 kHz=31 VFP=10 VSW=9 VBP=30 Hz=50
VESA detailed timing:
PClk=27500,00 H.Active=704 H.Blank=176 H.Offset=40 HSW=72 V.Active=576 V.Blank=49 V.Offset=10 VSW=9
Linux modeline parameters:
"704x576" 27,500 704 760 832 880 576 586 595 625 -hsync +vsync
WinUAE and Hoxs64 perform brilliantly with this. You just have to tune them up a little (for example, in WinUAE, enable V-Sync and use "no filter"). Just load Giana Sisters (in both emulators) and see how the title screen scrolls.
For the bloody-perfect-smooth scrolling, however, the most important thing is the emulator's ability to slightly alter the overall emulation speed, to synchronize it with the video refresh. Why? If you try to emulate a 50Hz system on a 60Hz display, you will see those annoying repeated frames. There will be many each second. As your display's refresh rate gets closer to 50Hz, those repetitions will be less and less. When it's very close, you might have (for example) 1 repetition each minute (or one lost frame, if the refresh is now lower than 50Hz), because those refresh rates are numbers with a decimal point and it's very difficult to create perfectly matching video modes.
Some of you might have heard about GroovyMame. This version of MAME is thought to be used with arcade monitors and TV sets (which have variable horizontal frequencies around 15KHz). Well, this wonderful software can alter the emulation speed as I explained above, but first, it will try to tweak the video mode itself, after choosing the one that's closest to the game. I use this with my VGA monitor and it works wonders with many of those 60Hz arcade games.