I'm a longtime lurker and only a half competent battler, but I've been experimenting with sun teams lately and I've actually been really impressed with Jumpluff as a dedicated Subseeder over Erufuun. I run
Jumpluff @ Leftovers
252 speed, 188 defense, 64 special defense
Sleep Powder
Encore
Substitute
Leech Seed
Which is basically the Subseed set posted in the Sun topic.
It doesn't seem like it, but Sleep Powder is a HUGE deal. For Subseeding to really be effective, you always want to start with either Leech Seed or a Sub up. You're most vulnerable when you first set up the Subseed cycle. If you Sub and the enemy breaks it on that turn, well, you're shit out of luck. If you Seed and the enemy attacks, well...
Sleep Powder lets Jumpluff bypass that completely. As long as it doesn't miss (and it might), you can freely start the Subseed cycle without worrying about a single damn thing. Jumpluff's so fast in the Sun that it might as well have Mischievous Heart (unless you're up against other Mischievous Heart users), so you can always get the Sleep Powder off. After that, you're in the clear. I'm no good at team construction, but Jumpluff's saved my butt tons of times. Starmie? Who cares. Ononokusu? Who cares. Scarfchomp? Who cares. Deoxys-S? Who cares. As long as it doesn't have more than 700 speed (and the only thing that does is Scarf Deoxys-S, which needless to say is absolutely ridiculous), Jumpluff can take care of it - and it can only do that because of Sleep Powder.
Of course, that Jumpluff also fails against Taunt, other Mischievous Heart users, Sleep absorbers, Ice Shard...well, it's not perfect, to say the least. And it wouldn't be inaccurate to say that Sleep Powder is the only thing Jumpluff has over similar Erufuun sets. But Sleep Powder is massive.
At least in my experience, Jumpluff's an incredibly good all-purpose check, and its Subseeding set has got a lot of merit compared to Erufuun. Erufuun's still better overall, but Jumpluff's got its own perks, and significant ones too, not just gimmicks.