The Mad Dog is a pretty solid mech. The main complaints come from it being a 'heavy' mech at the low end of the class, thus drawing comparisons to the Timby and Summoner, which have advantages based on their higher mass.
One of the Mad Dog's key advantages, especaly under BV1, was that it had a few veriants that were really terriffic values. The Prime, with its twin LPLs, was just 1871 BV, which is less than many Stormcrows and way under any Timber Wolf or Summoner worth having, despite having good accuracy and with the LRMs good power in close (I like to use the LPLs at range, and the LRMs and MPLs in close, since the LRM's don't have the ammo to spend at range and the mech can't stand the heat, but they offer good damage and crit seeking in close, with no minimums). The A was an even better value, at just 1510 BV, less than some very high end lights and most good mediums, for a mech with a PPC and LB5 for range, and a huge brace of SRMs in close. BV2 has evened things up a bit, but both thouse mechs are still some of the better deals.
I don't dislike the C the way may do. Yes, its silly innefficant, but no one wants to mess with two head cappers, especaly when its got so much excess heat there's no way to slow it down. The max amount of heat that can be added to a mech is 25 with two engine hits and 15 from plasma and infernos and flamers, on a mech that can sink 24 heat and generate at most 4. The resualt is that at worst, the Mad Dog can fight on for several turns, and most of the time if it can dodge the plasma for a turn it will never feer heat at all. In this new age of heat weapons, it is an asset.
The B is one of the better veriants, but I always found it was a poor value, because of heat problems and because of its role. A big slow mech with a lot of armor can plod away to close and fight at a lot of ranges, but the Mad Dog has speed to specalize a bit, so there's less need to have such distinct brackets as the B does. I prefer the Prime over it.