We actually have all of the expansions. They add a small but non-trivial element to the game. The additional powerplant deck also helps; otherwise, you begin to memorize the plants and know to wait until 25/26 hit the board and whatnot.

If I have a complaint with Powergrid, it's that our group has collectively opted into a strategy of delaying the start of phase 2. Sometimes this grinds on interminably such that we skip it entirely, and then enter phase 3 with giant cash hordes and bizarrely high priced powerplant auctions. It's still pretty fun, but sometimes feels a bit broken.

I've seen that a lot. Part of the reason can be plant starvation -- I'm not going to do a big build if I can't power them, so Benelux helps. Also, it helps to select regions with high connectivity (low diameter). If the one player who wants step 2 can't reach the only open space, there's a stall.

I do wonder if the rules could be tweaked to give some reasonable reward to a step 2 starter.