It is an alternative rock record with largely confessional lyricism, addressing themes ranging from adolescent drug use and revenge to perseverance and religion.

The album spawned several singles, including "Getting Scared", which was featured on the soundtrack of the horror film I Still Know What You Did Last Summer, "Shine", "Come Here Boy", and "Oh Me, Oh My".

Some critics dismissed the record upon its release as derivative of the work of fellow singer-songwriters such as Tori Amos and Alanis Morissette, while others praised the album for Heap's vocal performance and piano playing.

"[4] The album's opener, "Getting Scared", is a "vengeful"[9] track described by Gil Kaufman of MTV as "A spare, creepy tune anchored by a thudding drum-machine beat, chaotic piano and blasts of industrial noise".

[10][4] "Come Here Boy" is a "sensual"[11] piano ballad written when Heap was 17 years old about her music technology teacher at the BRIT School.

[9][8] Writing for Tulsa World, Thomas Conner wrote, "Heap has all the restraint Alanis Morissette didn't bother to learn...Her use of plunky piano makes tunes like 'Sweet Religion' shadow even a few Tori Amos standards.

"[1] For The Irish Times, Joe Jackson wrote of the record that there was "something fascinating" about Heap, noting that "the real power and poetry [on I Megaphone] probably stems from her semi-strangulated cries, the rush of crushed chords on the keyboard, the way her voice soars without restraint.

[9] Tom Demalon of AllMusic described I Megaphone as "A compelling album chock-full of engaging melodies delivered in a memorable voice," naming "Angry Angel", "Candlelight", and "Come Here Boy" as highlights.

[11] Eric Hiss of The Standard-Times wrote that the album was "a potent sonic cocktail that moves from chunky grooves to classical hybrids and careens back to sinewy guitar riffs" and "a soulful, intoxicating blend of pop", adding that its songs "aim for impact".

Farrell referred to "Getting Scared" as the "star pupil" of I Megaphone, and called the album "refreshing and even surprising" compared to her later work.