It really depends on the company as said, first line can be a scripted affair with pretty much no thought involved, or it can be much more involving, for example, the first point if contact scenario mentioned above - I worked for a large organisations where there was no 2nd or 3rd line, there's just a single point helpdesk backed up by specialist teams, server, network, on site techies, etc.
This is probably the sort of thing you want, as you learn a lot from the other teams that you can use to increase your first time fix ratios, and you get to chair conference calls between various teams to get to the bottom of an issue, so you get some exposure to the ITSM side of things, incident and problem management, that kind of thing.
But like I said, it depends on the company structure, 1st line can literally mean what I call 'logging and flogging' which won't be much fun, although at least you can say you have experience in a commercial IT role.