A few remarks on Abu's post:
1- Using the EPG-importer the box will not be 'sluggish' (at least I never noticed it on any of my boxes). One even can exit the plugin while download is in progress, and not even notice things are happening in the background.
2- Cross is the plugin to use for reading Open-TV data (i.e. from sky UK/IT/ Ausat); EPG-importer is better for using XMLTV-import. You can use both, but not at the same time.
3- In practical use it is impossible to prevent (some) double entries: not all services are covered by Open-TV & XMLTV, hence many people will also use EIT (or one of the other embedded EPG-readers). And as these can only be switched on/off globally (not per service), those services also covered by XMLTV-import can (sometimes) get double entries.
4- As ABU said 'EPG-refresh' is good for automated reading EIT (and others) from services.
All in all: many will (or should) have 3 plugins to get all available EPG-data in their STB. Make sure these plugins don't run together, but after each other. This can also be done at night time; if you usually get your box to deep sleep powertimers can be useful.
Set a wake up timer; run cross 5 minutes after that time, then EPG-importer (maybe during 10 minutes, depending on the number of sources), then EPG-reflash (duration will depend on number of and time on services) and the again a power timer to go deep.
One more thing: the data for the XMLTV-importer is only grabbed once a day and will normally be ready around 08.00 GMT. Please set the plugin to a 'strange' time (like 08.07) to spread host server load as much as possible (the plugin is massively used, world wide).