After seeing the episode, I now totally understand why they saved this arc for last. It's not just because Haruka's a popular character, but because her story deals with graduation, and the underlying theme is nostalgia, saying farewell, and moving on -- just like we're all going to have to do. So it's perfect for a conclusion to this show (omake OVA notwithstanding).
Other than that, I have to agree with the general consensus here that this was probably one of the best episodes of the show. It's actually funny because, despite being one of the more bold and adventurous characters, "Haruka in love" is actually quite bashful too. That's why they had to introduce Jessica to provide the little bit of extra push that Haruka herself provided in the early part of the first season (so it's no surprise they they're practically twins). Of course, no surprise either that Jessica's extra "forwardness"... and her extra bust size... are attributed to her being a foreigner. Ah, stereotypes...
Also, going back to the shack was a good call-back. Not all the other arcs had such obvious call-backs, but this one fit in really well.
Well, the ending of next week is pretty much telegraphed: Haruka graduates, and Junichi proposes... but I'm looking forward to seeing it play out anyway. Should be a fitting ending (again, with the OVA to come).