Thermal protection is a very important consideration; too thin and you're cold at depth or too thick and you have to carry lots of lead and you'll cook in your own sweat topside. I dive a 5mm one-piece June through late October, which allows me to wear less lead but I I finish some dives a little chilled. I've found that as long as I pull the top down and get dry inbetween dives, I can go all day. A good hood, boots and gloves are very important to the whole outfit and should not be overlooked.
Cold water regs are important as well. Sherwood Blizzards are very popular in Maine; cheap, reliable, easily serviced, and availible at dive shops throughout the state. I 've had my Blizzard out in 42 degree water and down past 90 feet without any problems. I recently bought a Zeagle Flathead 7, but will keep a Blizzard as a backup reg.
Due to a lack of funds, I have yet to make the switch from AL80s to steel. Would I like steel tanks, yes. Am I going to give up diving until I can afford steel tanks, no.
If you're considering a weight integrated BC, make sure that the one you choose has enough capacity to carry all your lead (for both your wet & dry suits). Also, having a BC which will easily adjust to your different wet/dry suits is important. Then there's the whole BP/W option to think about as well.
Keep talking to local divers and shops about what works for them as far as gear. For the most part, the LDSs in Maine will steer you in the right direction.