(The following is heavily my opinion, You have been warned, so don't trot out the guns.

)
Well, for any music game, the further up you go in difficulty, the more... technical the charts get and the more you can really tell that the charts were designed with a specific button layout in mind. In Trilogy's case, off the PSP series.
I'll give you an example. Some 5key/7key charts are very obviously NOT designed for the O2Jam/DJMAX Online style with spacebar for the center. They're made for two buttons covering the center lane with some ridiculous center lane spammage (e.g. Higher) There's absolutely no way you're going to do that without two buttons.
I do realize that that doesn't exactly void the design of the MUSE ON Controller seeing that it has 8 buttons, but my point is - you design gameplay around a base. Trilogy's base has obviously been the PSP series, so trying to force it onto a controller without a clear L/R split (which isn't even symmetrical in 8key mode, mind you) seems just... tacky to me.
I think the crux of my personal beef comes to how DJMAX Online was. You had sdf<space>jkl and <shift>zsxdc<space> both 'officially supported', and it was really obvious which charts were made for which. The harder charts were a complete mess because of this (although they did tend to gravitate towards sdf<space>jkl) and it really crippled gameplay, in my opinion. Here's a mid-level example - sdf<space>jkl gets
completely f'ing boned on charts like
Save My Dream (Sorry, couldn't find a less corny video)
After that, we go on to 2006 when Portable got released. The mess got even -worse- (my opinion
at the time - keep that in mind). Now you had the two control setups in DJMAX Online plus another one with 6 buttons. What defined DJMAX then? How do you tell someone what DJMAX gameplay is like, the way you can describe DDR as 4 pads on the floor, or IIDX as 7 buttons and a turntable?
DJMAX at the time sorely needed stability in terms of gameplay design. It needed a bunch of games following the same basic setup so that skill could transfer from one title to the next.
Now, fast forward to December 2008, and you have four PSP titles and an international rerelease planned, all following/expanding on that same basic control setup in the first Portable game. That's GOOD! Congratulations DJMAX, you just got that stability I was talking about. People who have played one title can relate gameplaywise to people who played another even without touching those respective titles.
It got even better when DJMAX Online was scrapped (lack of a better word) in favor of Trilogy, whose main gameplay type was 6key, and 5/7key were based off 6key/8key instead of the old spacebar-inclusive style. Now even the PC title shared the same control setup, and the mess that was DJMAX Online's competing control schemes was nothing more than a bad memory.
And then of course, indubitably, we suddenly have this MUSE ON Controller out of the blue which just.. I don't know, completely obliterates the stability I was talking about?
Is Pentavision going to design charts with this controller in mind? Design for both the PSP setup and the controller, and go back to the cross-setup mess that DJMAX Online was?
Sorry for the long rant, but I guess I've been thinking about music games a whole lot these few years. :/
Three things I hope you guys realize here:
1) I'm not begrudging people who bought the controller. If you have it, enjoy playing Trilogy with it, and kick ass, more power to you.
2) I'm not against the control setup. I love IIDX, I have a lovingly modded KOC (can't invest in a DJDAO at the moment) and I pop in the PS2 CSes quite often. I enjoy IIDX gameplay
because the charts were designed with the controller in mind, first and foremost.
3) Despite my DJMAX Online bashing, I loved that game as well. If a DJMAX existed today with a 7key sdf<space>jkl setup, I'd be all over it alongside the PSP titles. As it is now, I'm forcing myself to play Trilogy's 7key with asdf jkl; using space for Fever, because it's just... I don't know, good form (lack of a better term) I guess?
If you read the entireity of this post, I really want to say 'thanks'. I don't often allow myself to speak my mind, and I guess it's good to share my thoughts once in a while.
Last but not least, Technika plays different enough that it's in my mind a completely different music game with the same media (and I love the concept!), same way DDR and IIDX share some tracks. That's miles different from the we-can't-decide-which-buttons-we-want-the-players-to-hit mess I'm ranting about above.