Ok so I went a little nuts when the forum went down because I couldn't get spoilers from you guys so I watched everything from Broken Hearts to this episode (albeit at top speed).
I don't have a problem with the whole O/L thing because I've watched many Korean tragedies in my time. To to me it felt like Oliver never loved her enough. Just like she never loved Tommy enough. She was just never that person for him and so he bailed again after the flashback kiss.
I also thought it was an interesting contrast to the Broken Hearts episode where at the end Felicity left him and he said something like "oh but you can still marry me" and then telling her she can't be sure that he won't turn over a new leaf. He was wheeling and dealing with her and was desperate for her to marry him. He was essentially trying to chase Felicity into marriage like Laurel was chasing him at every opportunity.
Whilst it was totally sh@tty of them to kiss and plan the future one week after Tommy's death, I think it's very consistent with what Laurel had wanted her whole life and ties in with her telling Oliver he was the love of her life. He was. It's not rational but you can't help who you love. Just like he could never really love her back that way but Felicity is the love of his life.