Actually, I've had a lot of problems with my charger.
The Soneil distributor has been very good at taking care of things, but I burnt up two of their 7A chargers. I'm not sure what the deal was. In the end, I ended up going with their 5A charger which has a much more robust design (metal vs plastic case & better innards) and is incredibly reliable according to the distributor (who is an EV owner btw). Its actually a more expensive charger despite the lower amperage. I didn't really want to go to a lower amperage charger, but the distributor gave me the 'free' upgrade to the more expensive 5A charger after all my problems.
I haven't actually used the 5A charger yet as my car still has the front fender off from a deer accident a month or so ago. I haven't gotten the paint work done yet and the car is sitting in the garage ATM.
Despite all this, I still LOVE the Soneil chargers (I use them on my electric riding mower too). They work great and are fully automatic, just plug in and forget about it.
Charging the battery will warm it. However, at 5-7A its not going to warm it that much at all. If you want to warm the battery significantly I'd suggest a battery heater.