I've went through a stage in my early 20s of doing heaps of acid and I have mostly good things to say about it.
I never had hardcore visual hallucinations, a few visual artifacts like textured floors rippling slightly along with the usual coloured lights etc. However the thoughts and thought processes you have are fucking amazing and vastly outweigh any visual effects. I would say that I have had some of my best thoughts and inspirations while on acid and I have awesome memories of the trips I've had.
Socially you have a better experience on ecstasy, but the memories from acid last a lifetime. It is indeed true that you are a changed person after you have done acid (both literally in terms of brain chemistry and figuratively in terms of your personality and perspective) but generally it's a positive thing I think. It will truly open your mind.
One of the most important experiences of my life happened on acid. I was tripping and my non-tripping friend was driving us around, going to beaches and just mucking around late at night. She asked me what I wanted to do with my life; in a total thunderbolt moment of inspiration, the answer "to be creative" came to me, just like that. Acid gave me the total answer to my life's question: not to do or be any one thing in particular, but to approach everything I do from a perspective of creativity, ingenuity and lateral thinking.
The caveats: don't do it if you have any misgivings about it, or if you have negative stuff going on in your life, because that is a recipe for a bad trip. Do it with a trusted friend(s) the first time, preferably one who isn't tripping, in a safe and secure environment. Also don't do it too often - do it only occasionally and savour it. I made the mistake of going overboard and doing 4 1/2 trips in one week once, and it messed my head up for weeks afterwards (depression, mood swings etc) as you might expect. However sparing usage shouldn't knock you too much; I get worse after effects after taking E (the so-called "black Tuesday"). And don't do it just because your friends are pressuring you to do it - it's a highly personal, spiritual and almost religious experience and not to be taken lightly.
I don't do any drugs anymore but I don't regret doing acid one bit.