When we first started our home game, we had 2 players who had laptops. We found they took up too much space at the table and they took more time looking stuff up. My roomate and I (who alternate DMming) decided to ban laptops at our table. We have one player who keeps stuff on a handheld device (blackberry or ipod touch - I'm not sure) but he's organized and quick about pulling up the information.
4e just isn't complicated enough to need a computer (not like 3.5 with all of it's bonus stacking complexities and recalcuation of stats when your base scores change).
As for LFR gamedays - it seems our group is lenient with laptops, I've only seen a DM refuse a player his laptop once - and that was because he opened World of Warcraft as we were sitting down to play (another player had his laptop open only for his character sheet - but did start playing minesweeper after a lengthy battle and his character being out cold with no healers available)
EDIT: Oh and there's when I play LFR onlne - but that's entirely different
Everyone's at a PC then.