I honestly don't care whether they're funny or serious, but let's be honest here: REGARDLESS of how they turn out, we DO NOT need 7-10 minutes of every 22 minute episode (with the occasional full 22 minutes) being dedicated to Team Rocket failing at another idiotic plot. I know filler episodes are used to pad a season in any anime, but they have turned Team Rocket into the impossible: inter-episode filler. They pad individual episodes with their presence because they can't even fill a 22 minute time slot.
Personally, I like them whenever they aren't being bad guys and when they're being an
Enemy Mine. Jessie's appearances in Contests in DP (unlike AG where she was just a butt monkey the whole time) were great. The episodes where they join up with Ash and Co. to fight a bigger threat, but make it obvious they are going to try and backstab Ash are great.
Whatever they do with them, I'd almost like to see them as ascended rivals. They appear far more often than the stock rivals, but are clearly antagonistic, rather than friendly like all of Ash's rivals (sans Paul before the end) are. Let them continue to do criminal acts, and let them succeed every now and then. But for the love of all that is good, I don't think I can stomach them wasting 7-10 minutes of every episode anymore.