Contrary response
I have triple Weber sidedrafts and find them very liveable. My engine was built by Korman in 1980 to his stage 2 level, which includes lots of modifications. I believe you will not see the real benefits of the sidedrafts without at least a "hotter" camshaft. Personally, on an engine that was internally stock, I would go with the Weber 38 downdrafts.
My engine has somewhere around 100,000 miles on it and has seen autocross and driver school activity. I bought it used 19 years ago, so actual miles on it is unknown.
Drawbacks: runs rough and backfires occasionally at start-up. THis could probably be improved if I hooked up the choke linkage, but that is a little tricky. Once warm, it idles at 1100 rpm.
I have three sets of main jets and with the leanest installed, get 15-22 mpg with overdrive 5 speed. The carbs stay synchronized for years. Once set up properly, I contend that these carbs are very reliable, at least as much so as the factory Zeniths.
In exhaust emissions testing, I could meet CO standards, but the camshaft overlap kept me above HC levels.