The Sonatas are ok...
I don't have much respect for his work to be honest. Some of the most indulgent crap out there. Who writes a piece for 9 Orchestras or 9 String Quartets or 42 Gongs or 23 Flutes? I also don't think he's a particularly effective technician, which is very bad considering he's a spectral composer which is pure technique. I mean, just look at some of these pieces of his:
Hierophany (1973) recitation in 42 languages with 42 children
Do Emerge Ultimate Silence (1974/84) for 34 children's voices in groups with 34 spectrally tuned monochords
Byzantine Prayer (1988) for 40 flautists with 72 flutes
Dr. Kai Hong's Diamond Mountain (1991) for 61 spectral gongs and soloists
Where does one find 42 children of different ethnicities (let alone 34 children period) who will behave long enough to perform a piece they probably have little or no interest or emotional connection to. I found it amusing that he has this in his catalogue.
String Quartet IV
...................................for NINE string quartets!
The propensity for bizarre settings is something that I have been used to seeing with improviser/composer Anthony Braxton and his various projects (including a composition for 100 marching tuba players that actually happened in Manhattan last year and a older piece for four orchestras), but Radulescu steps it up much further. I really like String Quartet no. 5 (the only one I've heard). Inner Time II (for seven clarinets) has some excellent parts as well, but it's very lengthy (almost an hour....of ALL clarinets) and there are some high-pitched harmonic-based parts that make me feel like my ears are going to bleed.
His level of indulgence seems pretty startling and over the top, but I like his traditionally-instrumentated works (sonatas, concerto, string quartets with 4 players as opposed to 36) enough to continue checking out his stuff when it comes along. His work is nothing I would go nuts for, but definitely of interest. As far as the "spectral" composers who he is often grouped with in the literature, I'm much more interested in Murail's work.