This.
AS' April fools pranks are usually pretty button pushing and typically cheap to do. Doesn't take much effort to put moustaches on anime characters, add farting noises to the soundtrack, or run horrible movies. Most of the time, it's intended to provoke a response. Before they fell into the Room rut, AS' pranks were pretty much intentional or dirty tricks.
Last night wasn't a trick; it was a treat. I never got the sense that I was being punk'd - I felt like this was a genuine celebration of Toonami. If it were a joke, they'd have just run the same DBZ episode all night, or run an old Toonami open, then run The Room. This was a real Toonami block, with appropriate shows that either aired on the block or would have totally fit the block.
And honestly - they put way more effort into this than I think anyone expected. They got Steve to do voiceovers, they got companies to give them the rights to the shows for one night, they made a new game review, they made new promos (for DVDs), new intros, and more or less all new stuff. Yeah, they recycled old TOM 3 footage, but they made a LOT of new stuff to go with it. This had to have required more money and effort than running a crappy movie or adding sound effects.
So I never got the feeling this was entirely a joke. I felt like it was a lot more of a test to see if Toonami would work on Adult Swim. It's an interesting proposition that fits in my head. An AS Toonami would be freed from having to appeal at least partly to kids or the need to run CN's toyetic pickups. It would obviously be able to run less edited anime. It would be able to use coarser language. It could run M-rated game reviews, which most of the AAA games are these days, and give them an easy way to pick up advertisers. Most importantly, it gives AS' anime a separate, unique identity.
The trickier part is making a new Toonami that wouldn't rely solely on the nostalgic factor of a DBZ or a Gundam, and wouldn't have a DC show or something like Clone Wars to goose the ratings. It'd have to survive or fail with stuff like Bleach. I don't expect them to run Bleach with Toonami bumpers next week (I'd be thrilled if it did), and they'd have to do new TOM footage in HD.
Either way, last night was a resounding success, and the interest is more than there for a revival of Toonami. If it was just one night, then what a night it was. Either way, it's the best thing Cartoon Network has done in a lonnnng time. Kudos.