The Psionic classes... I have such a love hate relation with them...
Back in 2nd edition when I started playing DnD, me and my group were not fans of psionics... we felt they didn't quite fit in our vision of medieval fantasy and they looked pretty strong, so we felt they were more for the powergamers, something we were not (don't know if it's the case or not, that's just how we felt). So we never played them. Then came 3rd edition and we all pretty much skipped it (not because we didn't like the game, just because our interest were elsewhere, maybe a little burned out of DnD). Then came 4e, I fell in love with the mecanics and started a campaign. When the PH3 came out, my campaign was already started and seeing that it was mostly psionic classes, I decided to skip it, so I didn't buy the PH3.
Fast forward to 2 years ago. After maybe 10 years, I decide to get my 4e books out and start a new campaign. But before character creation, I decide to buy the books that I was missing, including PH3 and Psionic powers. Now, since I have the books, I decide to read on the psionic classes, in case one of my players wanted to play one. And I fell in love with their lore, particularly the Ardent. Someone that is playing with the emotions of others and using it for or against them, so inspiring. So much so that in my current campaign, it inspired the design of one NPC: Onyx, the most famous Opera Singer in the world, a Changeling Ardent. They can change their appearance to fit their role, play with their voice to sing like no other and use their ardent power to accentuate the emotions of the spectator so much that they come out transcended.
Sadly, mechanically speaking, I'm not a fan of the augment mechanic and point system. I mean, it looks okay, but I guess when it comes to 4e, I prefer to have a lot of options and well, Psionic classes (except the monk) just have less powers than the others. It looks like they would just use the same power over and over again, just with some variation to them. But since I never actually had a player playing one in my games, I'm just going with my feeling on this one. Maybe in game they are not so bad. I definitely would love to have one one day since now I love the lore about them... but looks like my players still prefer to stick with more classic classes... ah well, guess I'll use them as NPC then...