I have used 3.0 psionics for a wile and have not had problems with it. I do not use "Psionics are Different" option and if do not use the psionic combat system. As long as you do not use either of those systems then IMO psionics mesh well with the base magic system. I do not like the psionic combat system and have had trouble with it in a normal campaign. I have run a full psionic campaign where I used the psionic combat system and it worled well in that case. But that was mainly because every character was to some extent psionic and so it was a shared concern for the whole party. In a normal campaign I have found that psionic combat tends to be either not very useful for the psion vs non-psionic foes or very dangerous against psionic monsters (often well beyond what I expected).
I also do not require player to adhere to the flavor (crystals and such) of 3.0 psionics. In place of psycrystals I use mental focus objects of any type the player wants. IMC psions are basicly sorcerers who's power comes from inside themselves. As opposed to sorcerers, who IMC channel outside energies via their natural talent.
In my experience Psions tend to be rather focused characters with a relatively small set of [hopefully] useful abilities. To be honest I have had more problems with wizards than psions. Psychic Warriors have not be a problem for me and I often run them with custom power lists to fit the player's concept of their character.
In summery, I like the Psion and Psychic Warrior classes, the psionic feats and skills, and many of the psionic powers. I do not recommend the psionic combat system. I would not use the "Psionics are Different" option unless you want to put in a lot of work integrating psionics into your whole campaign world. I hope that is of some help.