I love Leipzig, so much so I go every year
Hotel wise you can't go wrong with Motel One (there are two in the city centre), the Ramada City and PentaHotel are nice. The Seaside looked nice when I visited friends there but with the event rates I couldn't afford it.
Attraction wise there is the Thomaskirche (where Bach was choirmaster), the Volkerschachtdenkmal (Monument to the Battle of the Nations). I'd also suggest going to the top of the Hochhaus (the MDR Tower) for the panorama terrace (3€)
For Rail/Air interest there is the large tram network, with some Communist Era Tatras still in service (though they are on borrowed time), the new CityTunnel is worth a look (the stations are something else!), there may still be some 143+DD workings but with more 442 (Talent 2) Deliveries they might be gone now (there were a couple around last June). Also take Tram 10 to the south of the city and see the preserved IL-62 just parked on a suburban street (I can't remember the stop but you can see it from the tram)
The city is very musical, with many festivals ranging from the classical (Bach and Wagner) to something rather darker entirely (Wave-Gotik-Treffen - think Whitby Goth Weekend, but 20 times bigger and without the fancy dress lot)
Resturant wise we tended to get some fast food in the Hbf (as it would be between bands at WGT) - the local chains are pretty high quality and cheap too. Did have a nice meal at a French resturant by the Thomaskirche but can't remember it's name.
Also for getting to Leipzig, there are direct flights with Ryanair from Stansted but most people I know go via Berlin and catch the hourly ICE to Leipzig which takes ~1h10 (this is our preferred option as Stansted is a pain in the bum to get to from here)
