Crisdean, I'd say EI business is solid across all three of the dimensions you're asking about. Aer Lingus generally get the basics right in business, and their crews are usually the friendliest around.

to me, their sweet spot for transatlantic business from the UK is being able to travel from regional airports via Dublin and saving the hassle and cost of going to London to fly. If, as you plan, you're already in London, I wouldn't recommend connection via EI it over a direct flight, but if you can get EI at a decent discount to the direct options that makes it worth your while to connect, I don't think you'll find much wrong with it.