Always liked the look of these too , heard of some mechanical problems and not sure on parts prices 
I had a Legnum(imported Galant estate) before the Omega. It's not as big as it looks, although the estate is pretty useful, and the car is comfortable. Interiors are well screwed together and durable, but look cheap and nasty, and the fake wood is laughably bad. The most interesting thing about the way they drive is that suspension travel is very limited. Otherwise, it's automotive valium.
Parts prices for Mitsubishis are horrendous. Galants also have a number of really expensive issues: the front wishbones are well known for creaking for a couple of days and then breaking, which always leads to bodywork damage plus the rear suspension is similarly complex; the tiptronic gearboxes are weak; the engines are gutless unless turbocharged, and also suffer from broken crankshafts(another Mitsubishi speciality); did I mention the cost of parts?
Avoid any GDi like the plague. That was the main reason for getting rid of mine which was starting to show all the usual expensive issues of a coked up manifold/head and knackered throttle body, both being very costly to sort. £15 each for the sparkplugs is a real kick in the wallet too. They're not even particularly economical, my 1800 was OK with me in it, but with passengers and/or luggage both the limited performance and economy disappeared. My annual trip to France cost the same in fuel as the Omega, yet the car struggled to top 90MPH. It's the only car I've driven that actually benefited from 98 octane fuel.
I can't complain too much though, I bought it for £300 and sold it for that a year later. I replaced the cambelt(£140 in parts with a trade discount!), changed the oil once and put 4 tyres on it.